Mail ist extrem langsam bei macOS Ventura 13.2.1

My Mail program is extremely slow on Macbook Pro.

Other support hints didn't apply or didn't help.

I have not much stuff on the mac and not many files, neither an unusually huge number of mails in/out.

I use only one acitve mail address and have only the icloud mail deactivated.

But I use it for work all the time and the slowliness really *****.

I have no explanation for this behaviour since my other macbook Pro and my airbook at home never had this problem and they are both much older meanwhile and had countless different mail adresses registered (same service provider Domainfactory - so this cannot be the reason for the problem either).

Can me someone give an advice what to do that I can understand as a normal human being without nerd-abilities?

Please!

In German or English okay.

Thank you