Is MacKeeper a good tool to clean my MacBook Pro?

First you need to properly identify the exact model of your Mac. Your first post mentions a MacBook, but your tag suggests a MacBook Pro, they are not the same thing.

There were 3 models of 2009 MacBooks, Early, Mid and Late.

There were 5 models of 2009 MacBook Pros, 17" Early, 13" Mid, 15" 2.53 GHz Mid, 15" Mid, and 17" Mid.

Click on the Apple's menu, "About This Mac," to properly identify your Mac.

enter the device's particulars here to find out:

https://www.apple.com/shop/trade-in?afid=p238%7CB89qqX8K-dc_mtid_1870765e38482_pcrid_78409092792302_pgrid_1254543333724235_pntwk_s_pchan__pexid__&cid=aos-us-kwbi---slid---product-

OS X El Capitan is the end of the line for that model:

No.

(216747)

No, it's junk.

There is no way that it's going to run any Mac OS version higher the El Capitan. So, no, the Apple Store won't be able to help you.

The Apple store would be able to help you...

... select a new model from those on display, to replace your MacBook Pro that is now about 13 years old, and can not be upgraded further.