I have a 4 year old macbook pro that has become very sluggish and slow. I get a lot of the swirling rainbow circle things when there are more than a couple of tasks running. It takes 5 minutes to restart. I have 'CleanMyMac' installed and run it regularly but the machine seems to get slower every day now. What steps do I take to restore my MacBook so it runs like it did or at least close to it when it was new?