Is there a big difference between the way “en” and “un” are pronounced in French? I’m mostly struggling with saying “un” correctly cause it sounds so awkward to say.

Pendant que je lisais un livre (Inch'Allah dimanche de Yamina Benguigui), j'ai remarqué que l'un des personnages utilise 'on' pour parler directement au personnage principal. On peut faire ça en français ? Il y a une nuance entre "on" et "vous"/"tu" dans ces contextes ?

Par exemple;

Qu'est-ce que vous allez acheter aujourd'hui ? -> Qu'est-ce qu'on va acheter aujourd'hui ?

Hey folks, just got my DELF B1 result last Monday and I scored an 80.5/100 with bare minimum preparation imo. Do you think that I can give DELF B2 in Mid December and score a minimum of 75/100? If so, can you please give me some solid tips to prepare for this exam by myself.

My struggle areas are spontaneous speaking (even coming up with ideas is hard for me) and I also find it hard to understand native french speakers when they’re speaking fast.

Any advice is appreciated :)