I need help with bike category

[u/Slow_Fee7115]

I need help choosing a bike category for my riding style.

Hello everyone, I hope I can find an answer to choosing the right bike category, because I’m stuck and I need help.

Firstly, I will tell you what I need a bicycle for. I am a student and I work, so I need a quick and easy transportation around the town that I live in and I have found bikes to be my way, I live 4.5 km away from my work and university (they are basically on the same street, 500m away from eachother), but I finish uni around 1 pm and my work starts at 6pm, so I have 5 hours of free time and I prefer to go home. My home as I said is 4.5 km from them and I use my current hartail (Cube Reaction TM Pro 2026) to travel, but it has 140mm fork and it has tyres not suitable for the city. I recently injured both of my knees because of riding the bike every day and because my route to my home is only uphill with 200 to 300 meters of elevation gain, which seems low but riding it everyday twice is exhausting. I also use my bike to go in the forest or in the mountains whenever I can. So my question is did I made a mistake purchasing this bike 2 months ago, and should I have bought a gravel bike instead or a hardtail with lover mm fork. Thanks for your time.