What DVC does when git merge is executed?

I have two git branches. DVC maps a data folder in both of them. When I go into master and merging with develop is correct that DVC does not add any new file inside the data folder created in the develop branch but leaves the folder as it is unchanged?

Yes, a git merge only modifies files tracked by git. If the develop branch modified the data, you’ll likely have a conflict in the data.dvc file, which you need to resolve. Once the git merge is done, you need e.g. dvc pull to see the merged data in your workspace.

I just tried, but I didn’t get any conflicts when I merged the two branches. In master data.dvc is still the same and is not the one modified in the branch develop.

Is data.dvc tracked by git? And did you record the changes on the develop branch and commit them to git?

Yes, in fact data.dvc is present on github. When i made a change in the develop branch i did dvc commit and then git add -A and git commit and git push.
The two branches has a different md5 string

In that case, I guess this is purely an issue with git merge. If the merge resolution picks the wrong version of data.dvc, you can fix it by manually checking out the one you do want.