Nouns ending in a are feminine, but there is a small group ending -ma that are masculine. Saying "la problema" is a very common error for learners.
¿Ha entendido el problema? · ¿Has entendido el sistema? · ¿Has entendido el programa? · ¿Has sentido el aroma?
Understanding the reason helps you internalise it rather than memorise it. These words come from Greek, where they are neuter.
Greek has masculine, feminine and neuter, and its neuter words look rather like its masculine ones, with a similar word for the. So on the way into Spanish, or into Latin, they were mistaken for masculine words.
Just as me can mean me or myself, te covers you and yourself, and nos covers us and ourselves.
Spanish does not say I get lost. It says I lose myself, the same way I get ready is I prepare myself, me preparo.
Yo me he perdido · Tú te has perdido · Nosotros nos hemos perdido · Lo hemos perdido (we have lost it)
The student produces "tú ha perdido" and the teacher calls it a contradiction. If you have chosen tú, the verb has to agree with it.
Sentir is also used for perceiving in the sense of smell, so have you felt the aroma? is a way of asking have you smelt it?
¿Has sentido el aroma?
The track opens by rehearsing this, and it is worth keeping as a drill rather than a memorised list.
haber → he, hemos || ha, has, han
Ask for the two vowels, get he and ha, then add the endings you already know.