A door handle to one of the rooms in my apartment has come loose. I cannot find an exact match online but it is similar in construction to this door handle.
The issue is that the lever part has come loose from the base. The mechanism itself is not loose from the door.
I cannot work out how to reattach the lever and I am wary of causing further damage by disassembling too much more. I cannot find any kind of manual or guide for this type of handle, but that may be due to not knowing the right terminology for my search. Here is how it looks: There is a central screw-like thing that should connect the lever to the handle - it wobbles and rotates freely but does not come out of the base. I can put the lever in place but not rotate it in-place without moving the whole handle.
There is a grub screw underneath but I'm not sure which part of the handle it is meant to secure:. Do I take apart the whole thing? Any advice is much appreciated.
It should look like this when assembled: