Problem when retrieving Keycloack token

I’m using Rest connector to retrieve token from Keycloack. I set proper header
{“Content-Type”:“application/x-www-form-urlencoded”}
And in request body I set needed parameters like this
client_id=something&grant_type=something&username=something&password=something

I’m getting response: Missing form parameter: grant_type error 400

In the Operate, body content is displayed like below with Quotation mark and maybe is problem if Quotation mark are added when request is sent
“client_id=something&grant_type=something&username=something&password=something”

I’m planning to introduce retrieving token by using Rest connector before calling needed API after that. Is there better approach to call API protected with Keycloack oauth token?
Can someone help with this problem?