What level can I achieve
If I completely learned and practiced all topics and grammar etc and I were able to use it correctly what level would it be?
The levels aren't directly correlated with the topics. They're just a different way of saying how many points you gained. You get points for doing lessons, practice lessons and translations. So, it depends on where you put your focus on. You can expect to have reached level 15-17 when you've finished all exercices.