Bad network quality

Eriks_Lizbovskis It sounds as if you don't have the best local network connection. The varying WiFi speeds definitely seem to be an indicator. They should be the same if you are pinging. 

A ping represents a few bytes of data, it can tell you some things but not everything. Plus it sounds as f you are pinging a local router, so you have many miles to go before you get to the Teams servers. Also, ping and network download speeds have known to be cheated upon by some Internet providers. They can see what you are doing and temporarily provide significant amount of bandwidth to make the test look good.

Ping and Internet tests all represent small portions of time when compared to a video call. 

Try connecting directly with Ethernet. That will help determine if it is a WiFi issue.

A Bad Network quality can be very transient caused by many things, such as someone else on your network starting to stream data, or other people at your ISP. 

If you don't need to transmit video, then don't. You should also be able to turn it off from coming in. Video uses 20+ times the amount of network than voice does.