Hi Axel,
Welcome to the forums! It’s great that you are concerned with right behavior.
You ask if it’s wrong or immoral for you and your girlfriend to watch movies in bed at your house. A good question. I know that you two are certainly able to refrain from immoral activities in that situation, but I don’t recommend it.
There are several reasons. For one, it may give family members the idea that immoral stuff is going on. We are to avoid even the appearance of evil.
For another, it;'s pushing your relationship too far too fast. If you get used to lying in bed together to watch movies, what’s the next step? Because relationships don’t stay static, they develop. And I’m sure you’re aware that your hormones are pushing you to draw closer together. In other societies, or other countries, you might expect to be married at 18. Probably not here, so it’s not ideal to give yourselves more temptation than you need.
Because temptation is a real thing, remember the devil prowls around like a lion, looking for people to devour.
I am sure you value your girlfriend’s chastity and reputation, so i urge you to treat her with respect and consideration. Don’t give other people food for unkind thoughts, and don’t put temptations in front of you that you can avoid.
Watch TV in the living room with your family, sitting on the sofa, or some equivalent.
God bless.