If you’re dating someone you work with, don’t make it obvious. Don’t go hang out with that person in your downtime, don’t touch each other at work, don’t talk about your relationship via work-provided avenues, like email or Slack. DON’T fight at work, for the love of god.
Similarly, if you’re dating someone you don’t work with, don’t invite that person to come hang out with you at work, ever.
I’m sure people here will tell you not to underdress, but don’t overdress, either. Read the room. Wear what other people are wearing. If you work in a hoodie and jeans environment you’re not going to impress anyone by wearing a suit. You’re just going to seem like a weirdo try-hard who doesn’t fit in.
Don’t get drunk at work functions, even if everyone else is drunk.
Don’t overshare about your personal life.
Speak up. You might feel like an outsider, and maybe you are, but no one else knows that from the outset. You construct other people’s perceptions of you.
Wear comfortable shoes.
Having said that, stay in your lane. Don’t talk for the sake of talking.
Don’t feel pressured to pay for things, like other people’s coffees or lunches.
Ask for help if you need it, but be smart about who you ask. Find a coworker who you get along with, or who has a similar background. Don’t ask your boss’s boss.
It’s ok not to love your job, but it’s not ok (for you and your mental health) to hate it. It’s fine to decide a certain company or industry isn’t for you, and to find a job doing something else. “Job hopping” has become the norm, with people only staying in a job for a year or two. This is the single most efficient way to increase your salary by non-trivial amounts. I know it can feel like you put in a whole lot of work and maybe money studying one thing, but LOTS of people switch careers multiple times in their lives. Find something that pays well and that you don’t dread doing.