Audacious

From your broken English, it's difficult to tell exactly what you are describing. Maybe you could find a tech-savvy friend who speaks your native language and ask him/her for help.

Hello.

Alright. A picture is really worth a good English >

Some parts of the player disappear by themselves. I have to click on eq or pl to bring them back.
And as you can see, the box eq is checked.
If i remember well, it only happens when i use external skins (and not all of them), but i'm not sure this observation is correct.

Thank you.

A new picture:

Here again, you can see the checked box for the absent playlist.

Does the same thing happen in a plain xterm session (no window manager or compositor running)?

How do i do that? :) I use Linux Mint 18.1 with Cinnamon. :)
How do i enter the plain xterm session? With a combination of keys?

Thank you!

If you're going to get into the business of reporting bugs, you need to get familiar with how your system works. Read https://en.m.wikibooks.org/wiki/Guide_to_X11/Starting_Sessions for starters.

I use Linux Mint 18.1 with Cinnamon. :)

These are details you should have mentioned in the first post already.

Anyway, when doing trouble-shooting, the first thing to test would have been to start Audacious in an alternative desktop environment, to check whether the problem may be specific to Cinnamon. Most distributions provides packages for other DEs as well as for simple window managers, which you could install and enable before logging in at the desktop manager login prompt.