Ask if your school can allow you to do year 2 Maths, Biology and year 1 Further Maths/Economics. Many of my peers who disliked one of their A levels dropped it, and took 2 A-levels this year, and the following year they are going to take the other one.
However, most schools have very different procedures, so I would be wary about this option as there may be timetabled clashes.
Moreover, I would only continue Chemistry if you have a real chance at progressing. If you have a A or B, you should consider continuing. You could alternatively use this summer to fix the grade. If you truly feel chemistry is a dead end, drop it.
The third option is retake all 3 of them. While it seems your "behind", assuming you have good grades in Maths/Bio, you would be chilling the year and only working really on 1