Oh, we were in a similar situation, I sympathise with you very much. We were saved by ordering special curtains here
https://rentcyprus.online, which completely block out the light. We took three of them and hung them wherever we could. After that we began to sleep better, the light really does not pass. It looks like nothing unusual, the fabric is quite thin. However, it works perfectly, now I'm trying to find a similar one in our country, but so far I haven't succeeded.