Hi klego,

> And i can't connect it with the base.

This part is beacuse your upper part is already a "thin wall" solid and you're then trying to connect it to just a single totally thin surface object that is not a solid.

You would probably need to model the bottom part also as a thick wall solid as well that matches the other one in order to get a proper combination between the 2.

But it's much easier if you want a bottom cap for you to not have created the cap right from the start, like for example revolve a profile like this:





Constructing your object this way will make a solid result with a connected bottom cap right from that start, it would be easier to make it this way rather than going kind of one separate surface piece at a time.

- Michael