And… so what?

When it comes to syntax and the construction of complex sentences (i.e. longer than a single clause, organized around a verb or adverb), the commonest device used in English is none other than the simple coordinating conjunction "and". As a rule, English speakers (and writers!) tend to use "and" more frequently than French people, even in elaborated texts. This means that writing long and complex sentences in English should be a little bit easier than in French! French students of the English language tend to over-complexify their writing with lots of subordinating devices (who, which, whose, of which, the [noun] of which, etc.).

Although that is not "wrong" in itself, the use of simple coordination is often felt as more genuine or natural by native speakers.

For example, a sentence like "I studied for one year in an American highschool as a teenager, which allowed me to improve my English greatly" is perfectly correct in terms of grammatical acceptability, but it sounds a bit "stilted" and unnatural, and native speakers would generally prefer a looser syntax such as "I studied for one year in an American highschool as a teenager, and this allowed me to improve my English greatly". So, whenever you can use coordination while keeping the message clear and unambiguous, just go for it!

Another common mistake which French speakers often make is to use the -ing form in cases where two actions are synchronistic (i.e. they happen at the same time), but where the one is slightly dependent upon the other. In such cases, the English language prefers mere coordination.

Example: "She left the room and slammed the door behind her".

Here, although the action of "slamming the door" has a slight logical dependency to that of "leaving" (it gives a kind of reason for her departure, and you cannot reverse the order of the two verbs in the sentence), English would use a form of "fake" coordination, as a rule. It would be very awkward/unnatural to write: "She left the room, slamming the door", or "she left the room while slamming the door".

It usually happens when two immediate actions are linked in time, with a small degree of logical dependency, especially with verbs of movement and/or speech.
Example: "When she saw him, she walked to him and said, ‘hello’". Here again, it would be very awkward to write "she walked to him (while) saying ‘hello’".

A last tip: When enumerating a list of people, things or actions, traditional grammar has it that you should introduce the last coordinating conjunction (and/or) with a comma. This is known as the rule of the Oxford/Harvard comma (depending on which side of the Atlantic you are!). So, for instance, you should normally write: "I sell apples, pears, and scoubidous…" 😉 (don’t forget the comma before "and"!).