What is the correct way to make changes to GIT (BitBucket + Source Tree)?

Question

git

Hello. Please direct the newbie in the right direction or indicate the errors in working with BitBucket + Source Tree. I reviewed a number of video tutorials, understanding is very difficult, everything is taken out of context, there are no answers to my stupor.
Task: get the code (repository) from BitBucket, make your edits in it and send it back (to the main member's account)
What did I do?
1) Accepted the invitation
2) Went to the BitBucket interface and made a Fork (should it be done at all?)
3) Made a clone in the Source Tree.
4) Made changes in the code of the downloaded repository
5) Committed
6) Sent via "Push"
7) I went to the BitBucket interface and see the changes made, but only on my kind of Fork. In the office of the main participant (who invited) this is not.
Questions:
1) Did I need to create this Fork at all in the beginning? And why is it needed at all?
2) How do I send edits to the main contributor?
3) If I want to periodically make such changes, do I need to constantly re-download the repository? Or once downloaded and it is stored and somehow updated (or should it be updated?). In order not to miss new edits from another person, and not to fill your own over it.
4) How is the process of transferring the updated code from GIT (BitBucket) directly to the server? With what toolkit? Can anyone do this or just the master who created the repository?

Answer 1

I reviewed a number of video tutorials ...

Here is the main mistake. To really understand what you are doing and why, you need to read:
1. Git Book / Git for a professional programmer
2. BitBucket documentation
If you have permission to make changes to the original repository, then fork is not required.
Using the Bitbucket to sync your fork to the origin...