new ipad cannot connect to the internet with 3g

hello everybody, I have bought the new iPad in Germany,because 4G is still not widespread in europe, I use 3G card, but it comes a lot of times that there is a signal from provider, andI cannot connect with the Internet with 3G, have somebody come with this problem?
Could you tell me how to solve it?
Thx!!

 

Bin in Österreich, auch kein 4g aber ich hab keine probleme mit 3G