Explain some points in git, how to proceed?

Question

git

I'm reading the progit book and I'm running into some questions about working with it.
1. If another developer made changes and uploaded to repo(bitbucket), I need to first download from repo(bitbucket) and merge with local repo, and after my work upload to repo(bitbucket) and another developer if he wants to make changes, do the same in that order?
2. I have a couple of branches, for example, if I am on the master and add git add files, are they added for all branches? Those. does it matter which branch I'm on in this case?
3. If I want to create a new branch for an adaptive, and for example, I made an adaptive for one block, do I just need to create a commit on this branch or a separate subbranch? I have not found how to create a branch in a branch. Tell me how?
4. Tell me what the numbers on the screen prntscr.com/bj4o94 mean , go on the sides for 2 @@ what are they for? there are numbers between them, there are minus numbers and are highlighted in red, and there are with a plus for example +25 and the line is green, and this is how I guess the red lines are those that are removed and the green ones are added. Only in the commet there is no such mess in the file itself.
5. Do you always need to work with tools for visual comparison and merge conflict resolution? If you merge automatically, it is not clear what goes where and how.

Answer 1

4. Tell me what the numbers on the screen prntscr.com/bj4o94 mean, go on the sides for 2 @@ what are they for?

This is the unified diff format , instructions for the patch program. The numbers mean the following: delete 463 lines starting from line 26 (lines starting with a space or a minus sign are deleted) and inserting 234 lines starting from line 26 (lines starting with a space or a plus sign are inserted).