OK, so today I updated W3 to the latest patch.
Out of all possible bugs I only have one, so it seems:

- I create a bomb, grapeshot or any other, and within the alchemy tab the game tells me that it actually has been created.

- Looking at the inventory, I find this bomb >>> "numbered" -1/7 yes, minus 1 of seven.

- I place the bomb in the right place, ready to use.

- Using the middle mouse button (after TAB/select grapeshot) I can throw the bomb >>>>

BUT

- hitting "E" when standing right in front of any monsters nest only gives me: "... you don't have the right bomb".

Now, I meditated, threw away bombs, saved and reloaded - nothing worked, I still get this darn message and monsters keep on happily nesting/breeding/monstering or whatever monsters do in functionable nests.

Any thoughs, anybody?
Thank you ...

Are you sure you actually have the right one for the nest? Not all bombs can take out nests, grapeshot and samun should do it though.

Isn't there a third one as well, or am I mistaken?

Grapeshot and Samum, both present, both selectable, both throwable - none of them works in conjunction with "... monsters nest, should destroy it!" (followed by "E" to actually do the damage).

Yes, sure of that!

Friends and neighbours >>> the problem still drives me nuts, and yes - I forgot to mark my initial post as question.

So please, if anybody has a kind of a clue why everything I create using alchemy enters the inventory with a minus ("-1/7"), and why I can throw bombs but not use them on monster nests (using "E" to make use of the selected bomb) >>> please tell!!

I don't have an answer, but clearly the fact that your inventory is being displayed as a negative number, and your inability to perform expected actions on said items, must be linked. It seems to me you need to find the common denominator. Do you have any (*any*) mods installed?

No, did not "feel" that W3 needed any mods.
Used for a short time software from CHU, but even this is not loaded anymore actually now.

About the "minus" sign: got this if I brew any consumable (like drink the stuff - Swallow and the like), too.
But this does not limit the use, I can still use any of them - several times in fact.
At some point I will have to meditate to refill - but this is the usual way to getthings filled up again.

Tried throwing the bombs at the nests using the standard method (middle mouse button), but this did not seem to work, even if I hit the target spot on.

Try starting a new game or sending your savegame to another player to test. Could be your installation, could be your character.

Well, I played W3 up until patch 1.06.
Stopped playing at this version number because of the many (and not always seemingly bugfree patches after that).

Then, yesterday, I updated to the current patch 1.08.4, skipping everything between 1.06 and 1.08.4.
The game (other then this topic here) works pretty well, just like before: no crashes and nothing out of the ordinary.
Except for the bombs issue (and the negative number of all things from the alchemy tab).

Guess it might be best to send a support ticket to CDPR, no other case with similar things is reported here in the forum (as far as I have seen).

Anyway, thank you all for bothering so far ...

What is this "software from CHU"?

Well, a trainer :).
Background to this: there had been a couple of discussions right here on the forum, all about the possible level cap of W3, about the statistics of all the gear at higher levels.

To see after this, I installed the trainer from CHU, pushed Geralt up to level 70, had a look at the characteristics of armor and weapons in this state - went back to normal playing after seeing all of it.

CHU ~ CHeats Unlimited.

There's your problem right there. Trainers are hacks, and are never 100% reliable. You have undoubtedly corrupted your save file.

If you say so...

Trainers usually add/replace some game files. Try to reinstall the game (check folder for trainer files after deinstallation) and then load savefile before using trainer.