When I started working in Japan, my Japanese was nowhere near good enough for the room I was in. What got me through was not vocabulary; it was a small set of phrases that signaled respect and effort. They bought me goodwill while the rest of the language slowly caught up.
The ones I leaned on
I am not going to pretend these make you fluent. They do something more useful early on: they show you are trying, and they keep interactions warm while your real ability is still forming.
Yoroshiku onegaishimasu — a catch-all for "please treat me well" and "I look forward to working with you." I said it constantly, and it was always right.
Osewa ni narimasu, for acknowledging that someone is helping or supporting you, opened almost every work exchange. Sumimasen did a dozen jobs at once — excuse me, thank you, sorry — and softened nearly anything. Otsukaresama desu, said at the end of the day or a task, is a small ritual of mutual respect that I came to love. And osaki ni shitsurei shimasu, for leaving before others, kept me from accidentally seeming rude on my way out the door.
Why set phrases matter more than grammar early on
Grammar lets you build new sentences. Set phrases let you participate before you can build anything. In a culture where the form of an interaction carries real weight, knowing the right phrase for the moment mattered more than being able to explain myself perfectly. They were scaffolding, and they held while I learned.
I am still learning, and I get things wrong all the time. But these few phrases taught me something I carry into English support too: sometimes the right small words, said with genuine respect, do more than a perfect explanation.