First of all that map has some bad pathing and balance issues, so dont panic if you lose in that map as ostheer.
About the stuart, you shouldnt really go sniper at that point, you should predict a light vehicle between 5/6 min in the game, if you saw the captain and if he had control of his fuel you can predict that the stuart is coming. I recommend you to go Pak first next time, and a well placed teller could seal the deal too because if the stuart hits the mine it will die instantly. Also you shouldnt keep your mg always in the same spot, try to play more dynamic with it and try to place sandbags and barbed wire with your pios at the start while caping and deny green cover with barbed wire. The sniper was ok but i dont recommend going sniper or light vehicles on that map because there are some good flanking routes and the pathing in that map is terrible for vehicles. Also you need to work on your unit preservation, when you see that light vehicle coming just retreat unless you are sure that you are going to kill it, because in that case you lost a squad but also the bleed doesnt worth. Remember to put your units always behind cover, retreat them in time, not overextend and i think g43s work better vs riflemen
I recommend you to watch these videos to improve your general gameplay:
