Why is the surfstick only using the 2G network?

I've been using a surfstick (Huawei) from Lidl Connect for almost a year. The D network of Vodafone is used. For some time now I do not get a 3 G network but only a 2 G connection, which makes a reasonable work with the Internet hardly possible. Feels like the times are remembered with the 56k modem. I also have the impression that the stick gets pretty hot. Does anyone have any experience and can give advice?

This is not the stick, but the network operator, and the base station. Yes, he is getting hot, but that does not hurt. That's why I went to O2 in Berlin, because you have the 5 Gigabyte volume reliably decent speed. In Tchibo (02 network with UMTS) 5 gigabytes have cost 19.99. The SIM card with 1 gigabyte start credit has cost 15.-.

Because of the speed setting instead of the Huawei software sometimes the freeware MWconn, with a little more options

http://www.mwconn.net/index_de.html

and / or change to O2 if you have no contract with Vodafone.

https://www.tchibo.de/internet-stick-p400134134.html

Thank's for the Tipps!