it would be good to keep biology (or chemistry) if you like it and can put in the work - while the test on monday might not go so well since you haven't done triple topics like the others, your teachers will understand that and you have the whole two years to learn those topics up to a-level standard. a science subject/background is good for anything, including law; it shows you have skills in practical work and are rational alongside other things. however, if you only took bio/chem because you got an a*, it's probably worth changing.
english lang and lit is also a good idea, but involves lots of reading; if you're prepared for that alongside 3 other a-levels, it's worth it.
you could drop both biology and chemistry and take english lang/lit and another a-level, but if you can't find another a-level to do and really want to do 4 or if you do indeed like biology or chemistry, you can take one science and do english lang/lit and you'll have a well-rounded set of subjects.