I had to immobilize my foot
so I can't walk for a few weeks
I got Covid-19
so I have to stay home for at least 15 days
I wanna buy a new smartphone
so I'll start saving money
My bedroom is a bit dark
so I'll buy a lamp
My dog is a bit sick
so I'll take him/her to the vet
I have a difficult exam tomorrow, so
I must/have to study