Internet keeps disconnecting while not using it / serving something on localhost

I’m a noobie here, so please don’t laugh at me :smiley:

I installed EndeavourOS two days ago, and I have a problem with internet.

Every time I start building an app (e.g. in JS or in PHP) that has to be served over localhost my internet speed falls down to 0.x mb/s. I have to reboot my OS then, reconnecting or stopping serving doesn’t help sadly :c

Can somebody help me solving this issue or is it just this distro’s problem?

I found out that it breaks when I open JetBrains apps. It’s not the serve problem. Can somebody help, please :c?

Thanks in advance :smiley:

Do you use any additional software in conjunction with JetBrains? Is there something like computer monitoring software? Or AdBlock of some kind?