Reformat part of an external drive

Hi. I have an external drive with four partitions. See attached. I want to get rid of at least one without disturbing others.

What I have: M1 Macbook running Monterey 12.6.5.

External drive "Container disk7" has:

1. An old partition with old backups of a previous machine. APFS Case-sensitive
2. A current Time Machine partition, in use for current machine. APFS Case-sensitive
3. Keep - A partition with data that must not be lost. Mac OS Extended (Journaled)
4. Data - A partition with data that must not be lost. Mac OS Extended (Journaled)

What I want to do:

Ideally: "Delete" #1 altogether so there are only three partitions. Have the Time Machine continue running, using not only current partition #2 but also able to make use of space that was formerly #1. Don't know if this is doable. DO NOT DISTURB #3 OR #4.

If I must: Erase both partitions #1 and #2, sacrificing my current TM backups. Instead, have a single third partition and start TM over using that partition. DO NOT DISTURB #3 OR #4.

Other possibility: ??

I'm not sure what to click on or how to proceed. Could back up my Data and Keep partitions first if necessary, although that would take many hours.

I'm a bit cloudy on format choices but I would think I'd want APFS for my M1 with Monterey...

Thanks!