Fiat Fiorino 147 engine problems

Hello together, I bought an old Fiorino 5 years ago to participate in a fun rally. Since then it serves every year for two weeks men’s holiday in summer. Now the big trip starts again in three months. He got new TÜV last year in July and stood since then in the garage. Now I got out in two weeks to move him again. I stayed after 20 minutes. Since then following behavior occurs: In cold condition he jumps immediately After about 10 minutes (as soon as it is warm) it goes out. After that it can start again but only keep it running if you keep it on gas. If you don’t do this, it goes out again immediately and doesn’t jump on. After about two hours I can start it again and the game starts from the beginning. Now it’s the 1.4 petrol engine with 67 hp with electronically controlled carburettor. No workshop with me still knows about it or wil So far I have only exchanged the spark plugs. I have the great hope to come here to help so that as a simple screwdriver I don’t have no idea of ecotronic carburetors in vain to renovate things. I certainly still forgot important information that I will always provide if they are needed to give me a help. Thank you very much.