Weird color dots and stuck while booting with apple symbol ...

Hello helpful People out there.....

Weird color dots and stuck while booting with apple symbol and the time line is close to half way.....

it also makes quite loud ventilation noise and this is already my second try to start ist again - last time nothing else after 6 hours - today I wait already 4 hours......

Any ideas or suggestions?

Thanks a lot for every idea

Best wishes from Vienna

Marlene