

Hello everyone!
I'm trying to grow a mango tree from a seed. I planted this mango 8-9 months ago and it has been growing slowly but steadily up until 1-2 months ago. Since then, it has tried to grow new leaves, but all of them die immediately. Now it has a lot of them on its tip and I don't know whether I should remove them or not?
Does anyone know what may be causing this?
I live in Poland, it's too cold to keep my mango outside during winter, spring and autumn so I keep it indoor next to a south-west window.