Yes it’s true. The amazing and interesting story began with Conquerer William and the Battle of Hastings in 1066, and even before there was some influence to English language by French. Through out the centuries there were influences in different degrees.
I have been speaking French fluent for years. Therefore the French language has an enormous impact on my understanding and learning of the english language. This is especialy truth for the vocabulary but for the grammar as well.
I think it is the same for english speakers learning French.
There is less similarity in the beginning but the more you progress the more you will appreciate the fact to know the other language. There is a historical reason to that fact.
Why does the english language have often two words for more or less the same thing or why are there a lot of synonyms?
When William the Conqueror became king of England, French took over as the language of the court, administration, government, culture (literature, art etc.), Later on there were other influences.
Of course mostly Latin and Greek as well and other languages are present in english language, too, There is a huge amount of information on the web about this interesting theme,
Although the fact speaking French helps me a lot, there are some tricky things to handle with (and I am not the only one).
The pronociation is different in english. Often words are formal and they are informal in the other language.
There are false friends, and words they are partially false friends and others have quite an opposite meaning.
Somtimes there are small difference in the meaning.
I will maybe share some examples in an other post or thread since I am involved and interested for a long time in the matter. For several weeks I’ve been reading the book “Honni soit qui mal y pense” from the author Henriette Walter. It’s an exiting story about the neighborhood and friendship between French and English language.
For advanced French speakers:
Honni soit qui mal y pense, l’incroyable histoire d’amour entre le français et l’anglais by Henriette Walter.