CS135 can be a difficult and demanding course. If you are a 1A student, you can drop down to CS115, the minor level version of the course. This must be done by the deadline - usually about 6 weeks into the term. CS115 covers the same general topics as CS135, but at a slightly slower pace and with less of an expectation of a strong math background.
For details about dropping down to CS115, including deadlines, please see https://cs.uwaterloo.ca/1acourses
Some important things to note from that page: