Moin Moin,
this could only solved with the Kunden Hotline
Hello @Andreei7, welcome to our o2 community :-)
I am sorry to hear there are issues with your DSL connection. As a first step I recommend to try out our o2 my service App on your smartphone. It guides you step by step through some troubleshoots.
If this should not help please contact our technical DSL department under the phone number that @schluej already posted. If you do not speak any german at all I recommend to call with a friend of <yours who does since we can not promise that you will reach an english speaking agent.
You my also try our service via chat or WhatsApp.
Regards,
Lars