very slow internet

Hi there, 

For the past week, I've had lots of issues with my internet connection at home. I thought it was because of the thunderstorm and rain but it's still going on. 

For a few days I didn't have any internet. Now the connection started again but I have~15-20 Mb/sec although I'm paying for 100 (home M). 

I've already check whether there was a problem in my area (Munich 80331) bit nothing has been reported. 

What would you advise? Is there something you can do on your end ? 

Thanks 

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