Place Value Practice I Have A Good Deal Of Trouble With Commas, I Never Know When To Use Them. Any Help?

I have a good deal of trouble with commas, I never know when to use them. Any help? - place value practice

For example, what happens with the use of a comma in this sentence
"At this time Polka music and playing accordion by the workers of the railroad German immigrants who left their mark in Wailea. Apparently, I should not be a comma after the word" worker "." Why not? And what is with this sentence: "The practice that the person's age, I think it reflects the value of a company is in the experience of life and longevity." What is the comma after "Age?" Thank you for your time!