Hi, there have been several questions on the relationship between the Gauls and Franks, and the "Frenchification" of the Franks; hopefully you'll find something to get you started in these recent threads

• What is the relationship between France, Franks, Franconia, Frankfurt, and Germany? - /u/trigger8888 provides an intro

• What happened to the Gauls when the Franks took over their land? - ever-prolific /u/deleted elaborates

• What is the date at which the kingdom of the Franks turned into the Kingdom of West Francia/France? - /u/NewYorkeroutoftown talks about the transition from "Frank" to "French"

• Approximately when did the "Franks" become the "French"? - /u/textandtrowel goes into more detail

Hey! In addition to the excellent responses linked by /u/Searocksandtrees, you may also find a previous answer of mine helpful-- it at least addresses the first part of your question.