how to use US phone number while using data from other country sim?

i’m spending some time living in spain for the summer. how can i send messages from my phone number, while also using data from the spanish sim. i also don’t want the sim to break my phone number, as before i had to text through my email, which no one had. it also broke group chats and it was very hard to switch back and forth between my number and the sim, and i couldn’t use both at once. is there a way to use my phone number, but stay connected via the spanish sim?