When i open something like Downloads or Pictures open automaticaly and the same folders to ''This PC''
I'm not sure if you're asking how to remove the two references to the same folder or how to stop expanding the folder when it's opened.
To remove personal folders from the navigation pane and the main pane of File Explorer,
This PC 'Folders' - Add or Remove in Windows 10 - Windows 10 blog
You could also simply right click the folder in Quick Access and select remove from the list - leaving only one reference under This PC
To stop expanding the current folder
Right click an open area of the navigation pane
De-select Expand to current folder