Well it depends. A beginner should be able to improve at a fairly fast pace. I've seen beginners (or almost beginners) add 20-30kg on their squat/deadlift and 15-20kg on their bench press in 8 weeks. But if you look at a world class athlete, adding 5kg in one year might actually be a normal improvement.
I will say that from experience an intermediate lifter should be able to add between 10-15% on their big lifts in a 12 weeks period. So about 7-10% in 8 weeks would be normal.
Now the issue might be that you are not making good choices for your assistance exercises. A chain is only as strong as its weakest link. Unless you are structurally build for a specific lift and have no muscle imbalance you will need to select your assistance work carefully so that you are directly addressing your problem area(s). But you can't afford to do too many assistance exercises either because you might not recover properly.
Yes you see to have bad levers for squatting, but that is not an excuse. It simply means that assistance work is even more important to you.
