Help I need technical support keep getting kicked to a solo session.

Hi I've played rdo on my 2Mbits wifi from my old tiny D-link router. I rarely had issues.

Recently I switched and I now have 100/100Mbits, though the ps4 gets a max of 11-25Mbits and 5-15Mbits in uploading (that's way higher than before). I also got a new router D-Link G403 4G-router N300.

The Internet works well in general EXCEPT when I want to play RDO in a public session (I want to play in a public session).

My MTU is fine. It's 1500 and I've tried other ones as well.

I've also played around with the DNS settings which didn't help. I've also tried changing the port forwarding thing on my router because rockstar said to do so.

I'm Swedish and my outlet is connected to the fiber line.

IT WORKS FINE WHEN I HOTSPOT FROM MY PHONE.

I've called the Internet provider multiple times with no luck. I dont know if they even understand the issue I'm having.

What can I do?

I'm practically illiterate when it comes to this. Any tips are welcome.