Hi,
is really a very problematic tip, instead you should use LAYMRG with Layer0!
(It doesn't make sense to delete things without knowing which things and possibly cause yourself unnecessary problems)
>>"Can anybody help me?"
a) "qselect"
qselect will select all 1. unnested 2. graphical object in the 3. current space only.
Three limitations and the reason why qselect is not the answer for all questions.
b) "I cannot delete a unused layer "
The Layer 'A-Pipeline-TL-2' is used, multiple times!
If you are running Version2020 or newer: Start PURGE dialog,
switch to non purgable item option, select your item (layer 'A-Pipeline-TL-2') and read about the references

431 objects inside two blocks are refering to this layer!
Both blocks are purgeable,
so the solution in this case is: Purge the blocks first and you are able to purge the layer then.
In a(nother) case you can't purge the blocks (because you still using them),
use BEDIT to edit the blocks and change the layer of theses 431 objects.