it really depends.
in my district, you can fail the first semester and not retake the course again if the second semester’s grade averages the first semester’s so that they have a passing average. but this doesn’t work vise versa. usually in most schools you have to make at least a “D”.
if you’re not doing well in math, always ask for help! maybe you can ask your friends who are making a good average in that class to help? or maybe stay after school for tutorials?
does this help a bit?
ps: i struggled in math, too.

usually in high school, a 70 or above is considered passing, anything below that usually requires you take the course again…

No, if you have a D you can go onto another math class, but not too far. Like, you’ll end up in the remedial version of the next class. As long as you can stay above an F you’re okay, but try to stay a little bit above a 60 because your final exam grade can bring you down below it and if it does you will have to retake the course!