Crescendo means progressively louder.
Forte is loud.
What sort of instrument? Am steg is an instruction to play a stringed instrument near the bridge, giving a heavier tone.
Crescendo and forte are from Italian rather than Latin specifically - and the former is indeed the language most musical instructions are given in.
However, in Latin, louder and heavier would probably be translated as clarior and gravior.
Musical expression instructions are usually given in Italian. "Am Steg" is German - the more usual instruction in Italian is "sul ponte". "Louder" would be "piu forte" in Italian, and "heavier" would be "piu pesante".