Problem with router at university room

Good afternoon everybody, I am new on the forum and I feel really good to be here, hope we can heal each other :D .

I am living in an university room which has internet access by ports on the wall where I simply connect my computer with a cable, however, to get internet I had first to register the computer MAC on the university network platform.

I want to install a router for the room so I can use wifi for my other devices, so I bought a router NETIS WF2411E, when I installed it didnt have access to internet so I registered its MAC on the network also.

Now it has access to internet, so I connect it to the ports on the wall on the WAN port and the LAN to my computer, however I am only able to open some websites (google, youtube and a few more) the other ones I cant access cause it says DNS could not be reached.

To solve the problem I made a MAC Clone so the router got the same MAC than the computer but I am still having the same problem, I can access some websites but just a few. When I try the Wifi on other devices it says "Connected but wihtout internet access" I have tried many things but I dont know what else to do, could you help me out with this please?

Thank you very much in advance, best regards.
Sebastian B