My laptop has become very slow

Hi friends,
I have the Dell laptop that train. So I opted to make him clean by removing temporary files with the help of CCleaner and doing a disk cleanup, but since it is compounded it has become super slow start again. It almost crashes all the time and found that several programs are deleted Microsoft office, Skype …
The problem that I have not created a restore point ahead and I don't want to opt for the solution of formatting because, I don't want to lose my data
What you advise me to do a system repair? Or you propose another trick?
Thank you in advance for your help.
