Larian Studios Forums Baldur's Gate III Baldur's Gate III - General some questions about spells

I have read the players handbook but some questions are still open:

- Some spells improve with level, especially cantrips get better at lv. 5, 11 and 17.
But what level? Character level, level of the class that gave you this spell or something else?
When multi classing, does it matter if the other class has the same spell too, is a caster class or cannot cast spells at all?

- All spells from different classes share the same spell slots.
So a sorcerer5/cleric5 has the same amount of spell slots like a single class character, but only half the number of different spells per level.
Paladins and rangers count as 1/2, fighters and rogues with spells as 1/3 when you multi class with a full caster.
+ How does it work when you combine those classes (paladin, eldritch knight and so on) when not having a level in a full caster class?
+ How does it work if you combine a caster class with a warlock, who has a completely different spell system (only a few slots, you use always the highest slot level, only slots up to lv5 higher level spells can only be used once per day, spell slots recover at short rest)

- Can you cast all spells with a slot of a higher level, even if the description does not mention an additional effect at higher levels?

- You cannot cast spells with somatic component if you have a shield or a 2h weapon equipped unless you have the war caster feat. Is that correct?