hy Vani!! 

To be honest, if you belong to unreserved category you cannot clear clat with just 80 marks. You need to get at least 120 above to get into to a good energy. Now to increase 40 marks in just 15 days, what you can do is to make a good strategy of attempting the paper and focus on only yours strength and just leave behind the weakness because in trying to overcome your weakness you might lose your strength also. So for now practice  the portion you feel like you can score well in such as legal or English. Just revise the things you have studied in GK a and focus more on legal section as there are chances of getting good marks in legal and logical as well.

 Try to focus on past year cat papers and solve them( two papers daily).

Last but not the least do not take stress stay motivated and practice well healthy mind learns fast.

I hope this helps you in your preparation!!

good luck for clat!!