Learn Italian: Quando ho troppo stress, divento nervoso. - When I have too much stress, I become nervous.

Yes, when troppo (too much / too many) is placed before a noun, it acts as an adjective and must agree with that noun's gender and number. Since stress is a masculine singular noun, we use troppo.

Is stress a masculine or feminine word in Italian?

It is masculine (lo stress). As a handy rule of thumb, foreign loanwords that end in a consonant are almost always treated as masculine in Italian.

In English we usually say 'I get nervous'. Why does Italian use divento?

English relies heavily on the verb 'to get' to show a change in state or emotion. In Italian, you cannot use literal translations like prendo (I take) or ottengo (I obtain) for this. Instead, you must use diventare (to become) for a change in state.

If a woman is speaking, does anything in this sentence change?

Yes! Because nervoso (nervous) is an adjective describing the speaker, it must match the speaker's gender. A woman would say divento nervosa.

If a friend says this sentence to me, how can I use this lesson's verbs to give them advice?