I find it hard to understand English... what can I do?
What I recommend is that you immerse yourself in the English language. Listen, listen, listen! Listen to English as much as you can.
You can listen to podcasts, there are loads of them on the internet or spotify. Choose podcasts suited to your level (beginner, intermediate, advanced).
Speaking of spotify, if you like listening to music, you can create a playlist of songs in English and follow the lyrics directly on the app. It's really handy!
Of course, you won't understand everything, but the most important thing is to understand the overall meaning, and then you can refine your understanding by looking up the different words in online dictionaries.
Watch netflix in VO with subtitles in French (beginner level), English (intermediate level), no subtitles (advanced level).
You can do the same for YouTube videos.
Give it your all, you'll see, you'll make progress, that's for sure!