Up to where is the game story going to get?

[Stoltverd]

Will the game cover everything up to this point on the LN? or only what has been covered by the anime? Or just the first season? Or...? Up to where?

[Hentaika]

It starts with the forming of the first party of Rudeus(Dead End) - which is ~volume 3 IIRC.

Considering that those are the characters shown - it means it's maximum as far as the Dead End party adventures go. Which is likely the extent of the story.
This would mean up to ~volume 6-7 or so.

There are also some entirely new scenarios made exclusively for the game. Likely to prolong the time with this party.

Aside of that - no details were revealed.