For most incidents that involve language, age is something to consider. For example if the players are younger children, (U10 and below, or there about), for any swearing, I’d be pulling specific players aside, involving their coach, and explaining why certain language isn’t acceptable, before potentially reporting as a safeguarding concern, (swearing by younger children can often suggest safeguarding issues at home). Then I’d issue sendings off if that swearing is offensive, insulting or abusive and wasn’t just general frustration. From what you’ve written though I’d assume you aren’t refereeing young children.
For anything above that, teenagers and open age football, I’d be applying a certain level of tolerance - from here it’s all about intent, tone and manner - if it’s some light banter or general discussion between players of the same team I’m fine with it - people swear in their use of language. If it’s to the level you have described - abusive, it’s a sending off, without debate. For language or actions to be a sending off offence they only have to be one of offensive, insulting or abusive, towards anyone. The actual threshold for what qualifies is different for everyone, but there tends to be some general accepted rules, for example phrases aimed directly at another individual, for example, “you [insert expletive]” would be offensive and worthy of a sending off. I would also consider words which are seen as slurs, or to have discriminatory connotations, rather than just swear words, to be a sending off regardless of the context they are said in.
As a new referee, what’s most important is that you don’t hold back in sending off players for language which is offensive, insulting or abusive. Once you’ve done it once it won’t feel as strange - but before that, just remember that your job as the referee is to enforce the laws of the game;
those laws empower you to take disciplinary action when necessary, so therefore you should do so. Talking to captains can sometimes be effective, but using your cards are even more so. Phrases such as “I don’t want to hear that again” can also sometimes be useful for incidents which don’t quite meet your threshold for OFFINABUS. Remember that for words or actions directed towards you, you can also caution and sin bin for dissent, (which is something else you’ll find a threshold for as you gain experience), but never caution players for something they say to another participant in the game, there’s very little basis for it in law.