K9-Mail is crashing, content of folders, esp. content of inbox is not shown imediatly but with a delay

Since latest major releases of K9-Mail K9-crashes somtetimes up on my Galaxy A51.
After opening K9 the content of inbox won’t be shown, it takes several time til my e-mails are visible. Same after changing folder or account.

Sorry about my rusty english - conversation in german would be more comfortable.

Thanks a lot in advance!

Turn off the “Show names from address book” option to make the list load faster