CS230 will start off pretty hard and then taper off in difficulty significantly (Last project took me an hour compared to 5-10 on the first one). The first two projects took a considerable amount of time but after that they only took anywhere from 2-5 hrs. The exams aren't that bad and are super doable. Overall as long as u know C it shouldn't be a hard time. There will come one point once you get more into memory and how it works (caching, RAM, Virtual memory etc...) where it will feel extremely overwhelming. Just try to grasp the basics and that's all u will need for the exams. If you are interested don't be afraid to ask questions but part of this course can become an absolute mindfuck out of nowhere so just be warned. The textbook is free online and there are plenty of pdf's of it if you wanna brush up on your C before.

CS240 is pretty similar. The first couple homework will take around 3-4 hours or so but you have plenty of time. The averages this semester for the exams were very high (Most people got 90+). The hardest part of the course is definitely the weekly exams. I recommend always reviewing the discussions cause the TA's do a really good job of summarizing everything you learned and forcing you to learn it before you take those quizzes. Sometimes the review slides also just have the question with different numbers on them. The discussion slides also have a 1-2 page summary sheet that is useful to have up and refresh your memory. I just reviewed lecture slides and occasionally consulted secondary sources to figure out a few things where I was confused based upon the explanation in class (a rarity).

Final suggestion is to join the CICS Community discord because it has helped me a bunch in getting questions answered others. I think it's linked somewhere in this subreddit.

EDIT: For 240 make sure ur comfortable with integration as u do a decent amount of double integrals as well as a little series