Hi, I was participating to BAM Boinc Stats in 2006, but now it is all a mess.

This is the page of my older ID: ID 11497

It shows points from 2006 to 09/2021

And there is a new ID, I am not sure what I have done: ID 106579500760 Maybe I renewed my ID...

It shows work since 2 months.

How can I merge these two accounts, and how can I tell Collatz to send new work? Because Collatz is waiting for my PCs with the old ID - and I am frightened to loose the 1 billion points.

When I look at your name on Colatz I see
User ID 7301
Collatz Conjecture member since 14 Feb 2010
Country Germany
Total credit 1,062,458,617
Recent average credit 3,834.44

Ok I see the problem you are running BOINC version 7.16.11 ... if has a expired an Certificate in it's Cert bundle. This affected a number of projects including Colatz

Upgrade your BOINC to 7.16.20 ... URL below and you will resume getting work.

https://boinc.berkeley.edu/download_all.php

Bill F

Thank you Bill for your help, and yes, I got work. But my problem is still there:

some Projects work for this John-Eff-Account: https://www.boincstats.com/stats/-1/user/detail/106579500760/projectList

and the other project (Collatz) for this John-Eff-Account: https://www.boincstats.com/stats/-1/user/detail/14497/projectList

Why? And how can I merge them? They share the same Boinc manager and are installed on different computers.

Looks like you got a split CPID. You can find numerous threads on this site how this can be solved, but it's usually complicated and can take a lot of time.
One of the possibilities is to sync your new CPID to the retired projects, check https://www.boincstats.com/bam/retiredProjects/