1. Finished all the tutorials but two
2. Could you explain or give me a link that would be helpful? Resets are when they can use an attack again without triggering infinite protection thing right? Sometimes my character pushes them back but they start a new combo before I can react.
3. I can never find any lobbies, like at all. None appear. Is there some sort of settings or stuff I need to make them show up? When I try making them no one show up
Number 2 right here shows you have fallen into the prime golden beginner trap number 1A.
You are thinking about the game and probably fighting games in general with a distorted view already, you need to stop thinking about the game as a combo trade off.
Let me try and break down the situation so I can try to explain.
The game begins , there is an opening gambit, each side picks a move, you can decide to do nothing and react but generally, especially in random games with strangers, both sides will either pick an instant offensive move or retreat into a defensive position, giving up space towards their corner but perhaps being in a good position to gain advantage after the opponents opening offense fails
Ok, so someone lands a hit right? This part is actually the most important, it isn't the combo, its the fact that someone managed to press their advantage or took a risk to actually attain the hit. This is where the game happened, from here, the combo itself is simply recognising the hit has landed, confirming into damage and ending in an advantageous situation.
Often times, this situation in Skullgirls will be a reset. Now understand, the opponent is GIVING UP guaranteed damage here, they are not just doing an attack that resets their combo for them, they are intentionally dropping their combo either hoping to catch you by surprise with you defense down, or to put you into a mixup situation they feel is stacked in their favour. Of course if it succeeds you are going to be eating a lot more damage, because they have actually just had the opportunity to perform 2 combos on you, not 1 as your post sort of seemed to imply. You were opened up twice, you had 2 opportunities to defend and get out of your disadvantaged situation here.
Of course as a beginner you are really going to struggle to see resets coming, Skullgirls has a very free system that pretty much allows you to drop a combo into a good mixup at any point. You will learn these things with time and experience. As a beginner you should be really taking the tutorial to heart, play games whether against players much better than you or not. Just make sure you are working on something in your games. Make a conscious decision to improve at something, even if its only one small factor of your play.
Combos you can learn in your own time grinding out in training mode, you need to get in game time to learn how to actually open people up confirm your hits.
Basically, try to recognise when you have advantage and when you don't. If you have any more specific questions don't be afraid to ask on this forum, people are glad to help, we always want more players.