There are multiple types of Giant and Giants normally aren't playable. Additionally Dwelf is not a race but looks like a mix of Dwarf and Elf.
As far as I can see, the system doesn't mechanically support mixed species but that doesn't mean that a character can not be mixed species for role-playing purposes, check with your DM that they are happy with it and if so, just add it to the description.
I'd recommend rolling up a Goliath, as they are descended from Giants and then in backstory say that one parent was a Goliath while the other parent was a half-elf, half-dwarf. That is probably the closest to what you have asked.
I'm just curious if it possible to make a character who is half Giant and half Dwelf.
There are multiple types of Giant and Giants normally aren't playable. Additionally Dwelf is not a race but looks like a mix of Dwarf and Elf.
As far as I can see, the system doesn't mechanically support mixed species but that doesn't mean that a character can not be mixed species for role-playing purposes, check with your DM that they are happy with it and if so, just add it to the description.
I'd recommend rolling up a Goliath, as they are descended from Giants and then in backstory say that one parent was a Goliath while the other parent was a half-elf, half-dwarf. That is probably the closest to what you have asked.
Piggy backing on R3sistance's suggestion going with the 2024 Goliath you could have your Gwelf lean into:
Coupled with being able to choose any 2 languages based on where you were raised, taking Giant, Elven and/or Dwarven gives you some options.
Backgrounds can also help strengthen this Farmer for Toughness gives you some Dwarven HP, or Sage for Magic Initiate for some elven spells.