Thanks for the reply, it never even occured to me that its might the fault of the wifi as every other device in the network works just fine.
I’m using the standard router issued by my ISP so its a bit hard to get good, non-german information about it. But further down i translated the part of the manual with all the technical specifications so maybe that helps.
The router is set to use both 2,4 and 5Ghz with the same name and PW. (this i cant change sadly) I was told to set the BSSID to a specific band as this might helps, but I could not find any difference.
Here my network settings
Edit: Connect automatically is normally on, just turned that off for troubleshooting
Translated Manual:
It offers the following functions:
Combination of five separate products in one compact device - a
EURO DOCSIS® 3.0 cable modem, an IEEE 802.11a/b/g/n/ac wireless access point, Ethernet 10/100/1000 Base T connections, VoIP Internet telephone connections and a firewall.
An internal high-speed cable modem for permanent broadband access to the Internet and other online services.
A powerful firewall for better network protection against unwanted attacks via the Internet. This supports stateful inspection, intrusion detection, DMZ, prevention of denial-of-service attacks and network address translation (NAT).
A broadband connection for up to 253 computers to surf the web.
All computers in the LAN communicate as if they were connected to the same physical network.
Four 10/100/1000 Base-T Ethernet uplink ports with support for half or full duplex connections with Auto-MDIX capability.
One IEEE 802.11a/b/g/n/ac WLAN access point, for mobile devices or for connecting desktop computers without a network cable. The speed of the wireless connection can vary depending on the distance.
The WLAN supports 2.4G/5G dual-band mode.
A secure wireless fidelity (WLAN) broadband connection for WLAN-enabled
devices on your network, e.g. mobile phones, laptops, tablets, printers, PDAs and desktop PCs. Routing for a wireless LAN (WLAN) or a wired Ethernet LAN; you can connect more than four computers via hubs and/or switches (not included).
An internal DHCP server for easy configuration of a combined wired/wireless LAN.
wired or wireless Class C private LAN.
Virtual Private Network (VPN) pass-through operation with support for IPSec, PPTP, or L2TP to securely connect remote computers over the Internet.
Internet Fiber Box Configuration Manager (CMGR), which provides a Graphical User Interface (GUI) for easy configuration of necessary WLAN, Ethernet, router, DHCP and security settings.
Translated with DeepL.com (free version)