develop branch is not usable anymore

A huge merge was done on 'main' branch. Therefore 'develop' branch is behind the main branch. All the merges have to be made in 'main' and 'develop' separately from feature branches. We want to go back to the following flow.

1. make develop branch equal to main branch
2. lock main branch
3. release main branch
4. merge only to 'develop' branch
5. yearly once, 'release' develop branch