Silent letters, linked sounds, and every word inside a real sentence.
French writes far more letters than it says. Final consonants usually stay silent, several different spellings land on the same sound, and words run into each other when spoken. This is why learners who score well on written tests can still freeze in a conversation — they learned a language that is written down, and were then asked to use one that is spoken.
No vocabulary game fixes that on its own. What it can do is stop teaching you words in isolation. Every answer here shows a complete sentence, and reading it aloud is the part that actually builds the ear.
"Je peux emprunter" does not come out as three separate blocks. Sounds link across word boundaries, and a silent consonant at the end of one word can wake up when the next word starts with a vowel. It is one of the main reasons spoken French sounds like an unbroken stream to a beginner.
You do not need the rules to start noticing this. You need to hear the same sentence patterns often enough that the joins stop surprising you.
Every French noun is masculine or feminine, and unlike German there are only two options — which sounds easier until you meet l'eau and l'ami, where the article is shortened and tells you nothing. That is why gender is worth learning with the word, from the first day, rather than added on later.
French makes you choose how formally to address someone every single time you speak to them. Vous for strangers, older people and anything work-related; tu for friends, family and children. Getting it wrong is not a disaster, but using tu too early with the wrong person is the sort of mistake people quietly notice. When unsure, use vous and wait to be invited to switch.
Recognising a French word on a page is the easy half. Producing it, with the right gender and the right article, is the half that counts. Once a set feels comfortable, change the language you speak so French becomes the source instead of the answer.