TL:DR: If the players know, talk about it above the table. Most likely, they will only know if you tell them, so if you don't tell them there is a problem, they will never know if you do a little bit of behind the scenes "movie-magic" editting to make things work out and be fun for everybody.

This is not gonna be the most popular piece of advice on this subreddit, and it certainly isn't gonna be for everybody or apply to every situation or scenario, but that's okay. Just because every new GM should hear this at some point, and I think it will probably help at least 9 times out of 10 with almost every post I see where a new GM is asking for help with something: "Talk to the party or player above the table and out of game." That's truly all there is to that, and just having a conversation like mature and mutually respectful adults can fix A LOOOT of problems that folks run into early in their experience of running TTRPG's.

Aside from that, the other piece of advice I offer for today is this: meta-gaming on the part of players is often seen as a bad thing, and it isn't necessarily the case at all times, but meta-gaming on the part of the GM is not inherently a bad thing.

Now, before anybody freaks out, let's narrow the definition of meta-gaming a little bit. When I say meta-gaming at this moment, I mean 'anytime one recognizes that they are playing a game and that as such there are certain things one can do with that knowledge.'

I am not saying make your bosses learn the heroes' plans and counter them or cheat to keep your BBEG alive (you decide those things for yourself, and either way just never tell them). What I am saying is that if your party is stuck, you can give them more obvious hints: have the answer literally hit one of their characters over the head, have an NPC discussion be overheard, give them a roll for something to remember an abstract clue or a detail they may have forgotten about. Whatever the issue or whenever there is friction at the table, you can find a way to fix that either in-game or out, and you can use absolutely any means and methods within your power as the GM to deal with it as you see fit.

As the GM, you can do anything or say anything and it becomes real for the world you run as soon as you say so, because you say so. Which means that you can justify the ingame thing later if they decide to dig into it, but you can fully metagame some solutions to stuff and just decide to throw out fewer monsters if the party has been taking a lot of hits, or you can add 10 to the damage of each hit when you wanna make a monster way more scary, and then if it starts to swing too hard towards TPK, you can just fully drop its HP to 1 and let whatever or whoever hits it next kill it. Those adjustments can all be made on the fly and nobody but you will ever know unless you tell them. You are the GM, which means that you are the Master of a GAME. Games are supposed to be fun, and that means if it isn't fun to you and your party, you can change the settings to whatever they need to be in order to make the game fun for y'all.

Every now and then, truly treat it like a PC game, and you have all the console commands and 'cheatcodes'. Because, for all intents and purposes, when you are the GM, you are basically like a coder who has full access to everything. So, good luck and good rolls, y'all. Have fun with it, and make sure they're having fun too, as much as you can.

When in doubt, just talk it out. Some stuff you should not leave to the dice.