Tortoise SVN update a branch anfter merging to trunk

Goodmorning,

Two devs, for example Bill and Max, are using tortoise SVN and they have created a trunk for a project (called "prj-trunk"); after that, they made two branch (with branch/tag option of tortise), one for each dev (called "prj-branch-max" and "prj-branch-bill").
In his branch Max made same modification and in the other Bill modify other file.
Now is time to merge in the trunk, so one dev use "merge" option of tortoise for put his code in trunk, and after that, other dev "merge" his file to trunk.
So the scenario now is that: Prj-Trunk with all modification, prj-merge-max only with max's modifications and prj-merge-bill with only bill's modification.
So what is the best way to update the two merge with all modification?
The first think I try is, starting with updated prj-trunk, make a merge with "merge" option pointing to "prj-branch-max" but tortoise SVN not find any modification (so the file updated from bill and merged in trunk, aren't recognized as new). I also try to make another branch with "branch/tag" option pointing to "prj-branch-max" but tortoise SVN return error (it say "already exist").
So what is correct way to do?
Thanks you

Resuming:

Ok please someone can tell me how to do the correct procedure starting from time #4 for update bill and max's brench??

When creating a branch in Subversion, it is created in the repository. The working copy is unaffected and needs to be switched to the newly created branch in order to change it.

Using the command line client and the conventional trunk-branches layout, one would issue the following commands; in TortoiseSVN, one would use the analogous actions:

touch A.c B.c
svn add A.c B.c
svn commit -m"Initial, empty files"
svn copy ^/trunk ^/branches/max -m"Create branch for Max"
svn copy ^/trunk ^/branches/bill -m"Create branch for Bill"

# At this point, working copy is still on trunk
svn switch ^/branches/max
vi A.c # make changes, etc.
svn commit -m"Max' changes to A"

svn switch ^/branches/bill
vi B.c # make changes, etc.
svn commit -m"Bill's changes to B"

# Now let's bring it together in trunk
svn switch ^/trunk
svn merge ^/branches/max .
# Resolve conflicts, if any (there shouldn't be any)
svn commit -m"Merge Max' changes"
svn merge ^/branches/bill .
# Resolve conflicts, if any (there shouldn't be any)
svn commit -m"Merge Bill's changes"

# Now let's merge those changes to Max' branch
svn switch ^/branches/max
svn merge ^/trunk .
# Resolve conflicts, if any (there shouldn't be any)
svn commit -m"Merge from trunk"

# Same for Bill

For more information on branching and merging, refer to the canonical resource on Subversion, the Red Bean Book.

Each user can add files first then commit to the main branch.

Max changed file1 and Bill file2:
Max needs to do : svn add main-repo (if new file for ex) then commit svn ci file1
Same thing for Bill

Then you just need to update your repo so to have the last updates files.

As far as Bill and Max aren't working on the same file, file0 let's say, you won't have problem.

But if they work on the same file, svn can't handle this case, it will only take the last updated file version.

So you need to first update