In professional contexts as a software developer you will manage just fine with just English. Free time context and true integration to society will require learning Finnish. But you can take your time with that.
I’m a Finn.
I’m a Finn.
What is the salary tax breaking point for 2020?
When do you need to have declared and paid VAT during 2020 if you are one a 3 month schedule?
These are basic knowledge questions for a freelancer with a Swedish Aktiebolag, easily googleable in Swedish but challenging if you don't know it.