Studying for an hour a week will only get you so (not) far. Intensity in terms of getting as close to immersion as possible as well as regular practice are vital.
The indefinite relative pronouns ce dont and quoi are used when replacing the indirect object of a preposition.
Knowing whether to use passé composé or imparfait sometimes depends on the meaning of the verb itself: some French verbs have different meanings in the passé composé and imparfait.
The rarest French verb form is the pluperfect subjunctive. It's a literary tense, meaning that it's reserved for formal, written French - mainly literature, but also history and journalism.
You probably know that 14 July is Bastille Day, but do you know what it's called in French? (Hint, it's not "jour de Bastille.") Do you know the history behind Bastille Day, or how it's celebrated in France? This page has links to everything you could possibly want to know.