and again it does not accept olemme kalassa Ruotsissa. I have reported it again
"kalassa" is an adjective or a verb in this sentence?
What case is it in Finnish?
It's a noun. Literally translating the sentence is: "We are in fish in Sweden". "kalassa" (in fish) is short for "kalastamassa" ("in fishing"). The case is inessive.
Is the same case that in merjassa?
Yes, the same one.