Telekom enables its customers to use LTE data networks in other European countries. This is also possible with Congstar, at least in Italy.
What is still missing are larger data packages - with 50 megabytes you won't get very far even if you surf carefully and use Google Chrome with data compression. But to upload a picture to Facebook it is enough, here you profit from the higher speed. Abroad it is still more advisable to use a Wifi connection - this is then of course protected by a VPN connectionotherwise you might as well hand out stickers with your passwords. Or if it's a holiday trip, you could do without the Internet altogether - it's usually the best way to relax.
The Congstar website does not provide any information, as it does for Lte use in Germany, but the same rules should apply as published by Telekom on its homepage: "Surf faster abroad with LTE„.