Spoken French and written French
CEFR B1 · part 2
edumaterial's parts within the level. The European framework does not subdivide them.
on, the French way to be impersonalUsing on where your language uses a passive, and building the être passive only when it…After a preposition, the infinitiveUsing en + present participle for simultaneity, and an infinitive after any preposition.After si, never the futureBuilding all three conditional types, and never putting a future or conditional after si.celui, celle, ceux, cellesReplacing the noun without repeating it, and always following the pronoun with de, qui…en France, au Portugal, à ParisChoosing the preposition by the gender and number of the place, for going and for coming.le mien, le tien, le sienAnswering «whose is it?» without repeating the noun, with the article in front and…The rule, in three lines
Spoken and written French are not the same language. In speech the ne drops, on replaces nous, questions are made by intonation and everything contracts. Neither is wrong: they are two registers.
The usual slip. Assuming the written forms are always safest, which sounds stiff, or copying spoken forms into an exam.
Why it catches you out. English contracts too — «dunno», «gonna» — so you take to this quickly. Your mistake is the opposite one: you go too colloquial in writing, because in English «don't» IS written.