I was wondering about this. Sometimes you eat and drink several things from the Inventory. However, I would expect the regeneration of the vitality to add up the foods and drinks that you take. Even, if you would have a parallel effect duration in time then it still doesn't seem to add up. For instance, if you drink something with an effect duration of 5 seconds and then take something to eat with an effect duration of 10 seconds, it seems to take the 5 seconds and leave the other 10 out. Am I missing something?

Yeah, I am wondering about this myself. I guess you cant just spam food for quicker or longer regeneration, but at least it should forbid you to eat while regeneration is in effect.
On higher difficulty, where Vitality does not regenerate upon meditation, every piece of food matters.

Btw I found also strange that there is no seperate hotbar for food and potiions. Its quite annoying in my opinion.

Haven't played much, but don't we have two slots for food bound to "R" and "F" keys?

Yes, but those same two slots are used for potions as well.

I hate those hotkeys, I kept accidentally eating food and drinking potions, so I swappend them to 1 and 2, and put weapon draws on 'r' and 'f' since drawing my weapon accidentally has no negative effects other than an NPC occasionally freaking out.

Exactly. Its annoying it allows you to eat/drink, when effect is still in place especially on harder difficulty.
The two slots for consumables used for potions and food are wrong in my opinion. I guess you can go to inventory and change whats in them during fight, but there should be better way.

I also learned something about how to fight the monsters. Its important to use the proper Signs and also make sure to Meditate once in a while to allow for certain potions to be filled up again alongside his vitality, though this is also subject to how much strong alcohol you have in you're inventory.

Agree, preparation is key. Always look to Bestiary for monsters weakneses etc. I am playing on Death March difficulty so its really important. On this difficulty Geralt does not regenerate vitality when meditate.