Learn French: Moi, je réfléchis au problème. - Me, I am thinking about the problem.

Moi is a stress pronoun. In French, it is very common to put it before je to add emphasis. It is like saying "As for me, I am thinking..." or contrasting yourself with someone else (e.g., "You might not care, but I am thinking about it").

What is the rule for the ending on réfléchis?

Réfléchir (to think/reflect) is a regular -ir verb. To form the je (I) version of these verbs in the present tense, you drop the -ir and add -is. This makes je réfléchis.

The translation says "about the", so why doesn't the French sentence use a word for "about"?

In English, we say "think about". But in French, the verb réfléchir is followed by the preposition à (to/at). You just have to memorize that French uses réfléchir à to mean "to think about" or "to reflect on".

Wait, if the preposition is à, where does au come from?