My S6 and Wifi don't get along

[91Fbh]

Hi. I hope some one can help me.

Since a few weeks my Galaxy S6 has been having issues with the Wifi at home. Sometimes sites wouldn't load until I disabled Wifi and enabled it again (I got some sort of "DNS" error) but other than that it worked fine. Now since about a week the connection while using Wifi at home has become really slow: Sites that used to take 1-2 seconds to load now take 20+, Skype calls have really bad quality and youtube will sometimes not even load or it will ask me to check my connection.

The important thing is:
- The Wifi is working fine with every other device in my house (Laptops, TV, Game consoles, other phones/tablets).
- My phone works fine when connected to another Wifi signal that's not the one at home (for example the one at work or the one at my friends/family house)

Any ideas of what to do?. I tried setting the DNS manually on my phone but it won't let me save (the "save" optio is grayed out). I also tried wiping the cache partition but it didn't help.
I'd like to leave a factory reset as my final option. I have a ton of photos, music and apps installed and backing all up would be a pain

Thx in advance




EDIT:

Ok so it's definitely a DNS issue but I'm not too sure on how to fix it.
I downloaded and app called "DNS Changer". Enable it and everything works fine again.
But I don't want to use that app, it has adds and has to be allways running. I tried setting up my connection with the static IP option using the google public DNS but it didn't help

 

[anon(632115)]

Rebooting your router would be the first thing to try

 

[91Fbh]

Rebooting your router would be the first thing to try

Already tried rebooting 3-4 times and it doesn't help.

As noted in my Edit of the OP, downloading and installing an APP like DNS changer works. The strange thing is that if instead of using the App I set the DNS manually (to the google one, the some one used by the APP) it doesn't work