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I want to build an Android app with overlay over the map, What layout should I use to achieve the result as the image?

enter image description here
Should I use fragments? but I want an overlay over the map activity. How can I achieve this?
So far, I have been trying, to add two buttons and on click of a button opens a floating map, but it doesn't give me this result, it resembles a bookmark bar on chrome with three dots on the sides which aren't what I want.

Not sure what you are going to do when user will tap on go back or any button or back press
but here i assume it that you are going to remove that white overlay and only map will be shown
if yes then you can simply use map in your activity/fragment whatever you like and white overlay should be created and shown using BottomSheetDialogFragment
to understand how you will create BottomSheetDialogFragment , you can refer this example
https://medium.com/#kosta.palash/using-bottomsheetdialogfragment-with-material-design-guideline-f9814c39b9fc

I think the best bet is using coordinatorLayout with a child layout that has BottomsheetBehaviour for the overlay. or simply BottomSheetDialogFragment if user isn't going to interact with map when the overlay is drawn up.
a layout with app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior" fits the picture. more on that here

Adding an image via button in Android Studio

I want to make an app, and there would be an list view with items and its info. In the right bottom corner there would be a button, and there is my question: how to add an image and some informational text by clicking on that button?

You really need more basics ... maybe you should start with a few simple tutorials. Whatever, for your problem you need a RecyclerView.

Creating a transparent, scrollable, flingable list without passing in a ScrollView for Android

I'm creating a platformer game for Android. However, I'm trying to overlay a transparent, scrollable list of text and (small) images in the title screen, outside of the game. Since the title screen was written in pure Java without the aid of XML, I'm looking to avoid passing in a ScrollView and changing the game's activity. Normally, I would build my own scroller programmatically, but I want my users to be able to fling the list to scroll, which I would have trouble implementing. So I was wondering if there was something for me to use. Also, I was wondering how other mobile games handle scrolling objects vertically with flinging? Do they build it themselves? Unfortunately, I can't think of a good example right now.
I'm looking to make the scrollable list transparent, so I can overlay it across a background image. Here is my title screen:
Title Screen
For example, when the credits button is pressed, the list will appear, overlaying an image in the background. (I haven't made the background image yet).
Sorry for the long post, or if this didn't make sense at all.

Image Click event in Java LibGdx

I am working on a Street Fighter Game. I need to have a character selection screen for the user. How can I do this character selection in Java libGDX? This is my image code. Can I do this using ImageClick event?
splashTexture1 = new Texture(Gdx.files.internal("assets/gui/Character1.PNG"));
splashTexture1.setFilter(TextureFilter.Linear, TextureFilter.Linear);
splashSprite1 = new Sprite(splashTexture1);
splashSprite1.setX(100);
splashSprite1.setY(180);

My suggestiong is using scene2d for menu or HUD stuff.
Check this out : https://github.com/libgdx/libgdx/wiki/Scene2d
scene2d is a 2D scene graph for building applications and UIs using a hierarchy of actors:
buttons
labels
sliders
text buttons
scrollable views (lists)
tables
your custom widgets
group of actors
You can add ClickListener to an actor. (In your case the actor is a Button)

You can do it in two ways. I'd recommend using both.
Common stuff
You can list images of all characters in a screen. And let the user select any one using one of the following.
Click event
Each image will have a separate ClickListener (If you have problem regarding that, you should search 'How to add clicklisteners to libgdx actors).
On clicking any image, the variable storing selected character (for the rest of the game) will be set with the image that has been clicked. And the screen is changed.
Keyboard event
One of the image will have focus drawn around it. The user can move focus around to other character images using arrow keys. When user presses enter, the character that currently has focus gets selected and the screen is changed.
Hope this helps.

I would recomend to use the Table-Layout from libgdx for it. Add an ImageButton to a Table and add an ClickListener to the ImageButton. Add the same Texture as up and down Texture and you are done. Maybe change it later so the user see that he has clicked a figure.
The Table gives you the ability to arrange those Buttons in the way you like and it's structured. Moreover it is easy to create a dynamic view, that does have new ImageButton for every new Texture you add to a folder for example. Just create a ScrollPane with a the Table of "figures" (which are the ImageButton with an listener) and you can add a bunch of it and let the user scroll down and up to check which he likes.

Android Button background Image changes back to state in XML

I have a simple soundboard which uses Buttons to represent the sounds. When a sound button is clicked. The background image is changed using the view.
Button butt = (Button)view;
butt.setBackgroundResource(buttons_on[media]);
buttons_on is a int[] representing the drawables of the buttons.
This all works perfect, but I also use a FragmentActivity to create a paged App. The App has 4 different pages which you can swipe through. When I change a button using the above code and swipe two pages to the right and than swipe back. The image of the button has changed back to it's default defined in the page.xml.
How can I prevent this behavior?
change the Buttons to ImageButtons and setting the src?
somehow prevent the page from reloading

Instead of doing that you should look at how to use a StateListDrawable. It will simplify your approach.