Mac OS el capitan mid 2007
you ask about monthly .maintenance, how and what program. my mac as slow and freezes a lot what can I do for maintenance and clean up
If you have a 2007 Mac, it should never had had El Capitan installed, Mavericks or even Mountain Lion would be appropriate.
El Capitan needs 2Gb RAM just to open properly. 4Gb RAM to run a couple of programs well, 8Gb to function well.
Every new OS requires faster hardware and more memory.
When OSX runs out of RAM it writes to the hard drive which is 1000 times slower.
About this Mac under the Apple Menu shows the Memory installed
An external FW SSD boot drive would be an improvement, an internal SSD drive would be much faster.
will tell you everything about your computer.
will show you how to install things.
will show you how much RAM your Mac can hold
https://www.macsales.com/ sells Mac SSDs and has video to show the difference
Start in SAFE MODE once a month (SHIFT key down at startup) maybe run ONYX
Google "mac maintenance site:macworld.com"