Hello everyone!
I'm really desperate to learn how to fix the anim on beds. I have tried many things but I really don't understand it and I've searched everywhere for tutorials and stuff but no luck. So now I've decided to ask here.

My question is how can I lower or raise the mattress and keep the animation? Here's how my test bed anim looks like...

Here is the bed with the wrong ani but with the mattress in the right place.




and here is another try. The ani is right but the mattress is floating the frame too




Thank you in advance.

First, the animation is not affected at all by how the mesh looks.

There are two ways of getting sims to use an elevated/lowered bed. In the simpler version, sims do all animations as if the bed were at normal height, like in your second picture, and then they "float" to the appropriate height. I believe this is done by moving the appropriate slot which tells sims the position of the bed. This does not necessarily look good, but is accepted as standard because the other version requires new animation.

The second version is making a new animation of how you want your sims to reach the appropriate height (e.g. use a ladder). You can study the loft bed in the Grand Trianon set to see how it's done, but please note that you are not allowed to clone their bed. This is the only elevated bed I know that uses the second solution.

Thank you Gwenke33! Yesterday I removed the frame from the package and it did what you told me on the first option (which I don't mind) and then I made a separate package just for the frame and it worked like I wanted to. So now I'm wondering if there's something going on on the joints messing with the frame itself.

I already tried to study the Grand Trianon but it's still a bit complicated and I wouldn't want to clone it either as I want my very own ^_^