@Sunshine

Yes, it's in wireless mode.

I updated the firmware now and keep you updated.

Have honestly never checked the support page and the integrated version check always returned that I have already the newest version.

Thank you for the note, that there is actually a newer version - was already wondering 

  @Sunshine 

Ok, the issues still persist.

My mother (with a different VPN than myself, using Cisco AnyConnect) was initially not able to log in, then it reconnects all the time.

After she was able to log in, I was kicked out and had to relogin in my VPN (using Windows integrated one).

Now I'm logged in and right now it seems to work fine from my side, but I think my mother still reports that it's slow.

Edit: Ok, I'm also having some connection issues/slower connection from time to time...

I just noticed, that in the Windows Event Log are many DNS warnings...

Looks like that's an issue.

But I'm not sure how to configure that best.

I had Google DNS (8.8.8.8, 8.8.4.4) set up on DHCP and on the internet option itself

(or a mixture of default and Google, I honestly have played around with it so often, that I probably had all permutations already).

  @Sunshine any other ideas or solutions?

It's getting a bit annoying .

Thank you in advance!