The way D&D works puts all socializing into the hands of stats/skills/Bonuses. This means that a social interaction like your character trying to sweet talk their way past a guard works like this:
Alternative variants to how to solve this:
These last two gives different ways for players to roleplay their characters and interact with npc's. They also create a lot more interesting and unique scenes than “Yeah we ran to the guard and I rolled a 20 so he just let us right through!”.
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Note: Personally I really don't like option A, and if anyone ask to play like that, I'd basically play it like the character is trying to act friendly with smiling or miming but not actually saying anything. And permanently give it disadvantage.
Optional would be that I just make up my own shit for everything your characters would say, which is going to fuck you over royally as I'll take every chance to make fun of your characters, but also potentially lock your characters in some nasty situations simply because you're locked by the dice roll and I decide the actual things you say as according to that dice-roll. (You seduce the Orc to give up his evil ways)