I think you're confusing us with the British.
Germans are careful about anything that could be considered antisemitic because of history but unless you go straight to Nazi slogans, there is no law that forbids you from being critical of Israel. Insulting someone can be illegal but that can only be applied if you insult a specific person, not a country and it's only enforced in extreme cases.
So unless OP plans to join a full-blown anti-Israel protest that risks getting violent, I don't think they have to worry about that.
Technically yes but realistically it only gets prosecuted in extreme cases. Like throwing feces at someone or distributing leaflets with your insults. If you just call someone an asshole, no police officer in the country will even bother with it. It's hard to prove who said what and the maximum sentence is extremely low.