Your computer has multiple cores? If so, that's why.

a) Increase Duels' priority in Task Manager.
b) Disable some cores in your BIOs.
c) Simply complete it while playing on a different computer/laptop.

Didn't make a difference. Not sure i want to ♥♥♥♥ about with my BIOS just to get some gold. even though i'm a massive completionist.

Other than playing on a different computer, there's not much you can do.

This problem with the Tutorials/Skill Quests have been reported since the game launched.
In the 2 years the game was being managed, they didn't find any solution.
And, there certainly hasn't been any work to fix this since the game was abandoned 2 years ago.

aww man what a downer. Do you think they will do anything for the next pack of magic cards to be released?

This game has been abandoned. There won't be any new content updates.
And, there haven't been any since 2017.

That's why Wizards released Arena, which is developed in house.
Arena is Standard-based, which includes {XLN/RIX, DOM, M19} and {GRN, RNA}.
Sometime before the fall rotation, there should be a non-Standard format, with {KLD/AER, AKH/HOU}.

shame! i like eldrazi I also really enjoyed the singleplayer of this game. The artwork etc.