Hope you don't mind us replying in English as it's the Community's official language.
The fastest way to clean a playlist out from unwanted songs is to hold the Ctrl key on your keyboard and press the A key. This command will select all of your Liked Songs. Once you're ready, simply press the Delete button on the keyboard and all the songs you've selected will be deleted.
Alternatively, you can click on a single song, hold the Shift key and then select another song for the end of your selection. All songs included between the first and the last song you selected will be deleted after pressing the Delete key.
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“Music is the strongest form of magic.” Marilyn Manson