All you will get on here is half arsed judgemental comments
I'm afraid he's right.
Everyone will just say how awful your ex is, and how it is not fair. But also, they will be right. It isn't fair. And you are being so fair - 600 quid a month in Poland is like £2K in the UK.
You are giving your all totally selflessly at the moment, and risking your life every second. I'd agree that your daughter has the absolute right to know and love her daddy, who is an amazing person. Nobody can deny you or her that.
I think you have to just ignore the ex trying to get you out of the picture, and try not to be hurt by it. You must keep visiting - just take no notice of her saying you don't need to, or you don't speak Polish, etc. And as for interrupting exams - 6 year olds don't have exams.
But also, when you get back to Germany, I think you need maybe to get sorted with some kind of permanent arrangement.
Looks like the only way you will get to see your baby is if you spend time often in Poland.
I know someone who goes every other weekend to see his kid in another country. He has a small flat in that country, and he always goes. And sometimes his kid comes over here to stay with him. You need an arrangement like that.
She hasn't actually tried to stop you yet - she's trying to put you off. But don't be put off.
I don't know what else to say really, because I just feel so much for you out there. You deserve all the support anyone can give you - not someone putting you off. But I guess if you can face Afghanistan, you can face this. Good luck.