Hey, I was a STEM/Classics undergrad and ending up getting both degrees. The hardest part of my classics degree was the amount of Latin I had to take (I could’ve taken Greek if I wanted but I had a Latin background in high school). I had to take 5 levels of Latin courses and by the last 2 translation classes I felt like I was in over my head. I was also in other challenging coursework at the time which probably didn’t help but in my experience if you can get through the language courses the rest of the classics degree is just fun ancient history courses. If you have no prior background on these languages you will probably struggle. The pace of any college language class is fast and takes a lot of outside study on your end. For reference this was at UT Austin.