Get access tokken with login in credentials?

Short answer no. The token is retrieved based on Twitch receiving the request from your application with your Client ID and Client Secret. This is essentially how OAUTH works - one important piece is never passing the password/account information for the person that you which to receive a token for.

The tokens do expire, based on their documentation. You will need to look at storing the refresh token and taking the appropriate action or requiring re-authentication as needed.