About my school life

I just* took my last engineering geology class**. l will take part in the final exam of this subject.***

l do not feel happy today because of our sun sport meet. l belong to the department of civil engineering so l need to join in the walks square formation. l think this thing is boring, but l need to practice it tomorrow afternoon****.

*I feel that if you're using "just," you don't need "Today" since just kind of implies that.

**I, personally, would use class over lesson. It's not incorrect, but most people I know use "class" to refer to lessons in school. 

***I don't see why you used "but" to connect you taking the final exam and you not feeling happy. Your original sentence makes you sound like you're happy to take your final but the sun sport meeting ruined that happiness. If that is what you meant, disregard my correction. However, if you meant you are happy that today was your final day of class but your sun sport event is ruining it, then your sentence needs to be revised. I hope I'm not being too confusing...

****For clarification, I would use "tomorrow at noon" or "tomorrow afternoon" depending on what you meant. "Tomorrow at noon" would indicate tomorrow at 12:00 p.m., and "tomorrow afternoon" would indicate any time after 12:00 p.m. tomorrow untol evening time, which is usually around 5:00 p.m.-ish.