For emails, you may try an IMAP copy solution, like this one: https://imapsync.lamiral.info/
As for /e/ or Murena, settings are here : Email Configuration - e Foundation - deGoogled unGoogled smartphone operating systems and online services - your data is your data
You surely will find Yahoo IMAP settings in their support pages.
PLEASE avoid using an online IMAP copy solution ! You’ll have to provide tour credentials, and your messages could be going through a server with unknown security level!
If using a PC email software solution (like Thunderbird), you could also use it to copy your emails.
Contacts are something completely different.
If you can export them in VCARD or VCF, you may try to import them in Murena Cloud web interface, or directly on your phone.
I’ll advise to try both with a restricted set of contacts, 2 or 3 of them (it is easier to delete).
You may also find some PC open-source programs to edit/organize your exported contacts.
It is a common subject of concern for beginners, you will find plenty of information using this forum’s search function.
Also here, please refrain using any online service.