Total Noob is Dismal at Heads Up, Requests Triage

So, I have been trying to play without depositing at Carbon and have played in quite a few of those FunStep things.

I have made it down to the final 2 in FS3 maybe 4-5 times but only won one.
Yes, it is a small sample size, but if you were to watch the final sessions, I seem to be on a mission to give my chips to the other player.

So here is what I have been doing and please feel free to laugh and criticize.

Stage Zero (three people left)
I fold a lot on the button to observe the tendencies of the two other people left, particularly the one most likely to be in F2 with me.

Stage One (if I start ahead by 5-10 BBs):
When it starts, for about 10 hands, I limp in from the button a lot, raising on the button pre only if I have a pair, A or K. I raise only if I hit the flop. I will call down or raise players that have been raising post-flop with less two pair or folding to raises. I lose some amount of chips this stage.

Stage Two
I start raising from the button about 50% of the time. If I get enough hands in the top half of hands, I will raise those. Otherwise ATC if I need to do it to bring the percentage up. I play anything middle pair and above pretty hard unless played back at me harder. The amount I call down or raise depends on cards and how the person behaved in Stage One.
I pick up a ton of chips here, it seems.

Stage Three
Then... something happens and I find myself folding almost every hand till I have very few chips and only survive through a double up.

The one time I did win, it seemed like the Stage Three roles were reversed. The guy just kept giving me chips every time I raised. I couldn't understand it.

Can anyone direct me to some resources learning heads up and/or lay out some beginner tips?
I guess my big question is, after you are done laughing, can someone tell me what the mysterious thing is that is happening at what I am calling Stage Three?

Sincerely,
Confused Fish

Stay aggressive is the biggest thing. HU, even a pair of 2s is likely to win. There will be times you lose, for sure, but long term, aggressive is key to winning.

Get agressive. Expand the range of hands you are willing to start with. When shorthanded a king or queen are as good as an ace.

If your opponent feels you are being passive he will push at you all the time. This is why your stack shrinks. Sometimes you have to take a stand with less than premium cards.

Stage Zero - You are missing a great chance here. From the button you have great position. You should be able to steal a lot of pots just by betting whenever it is check to you. Builiding your stack here gives you a better chance in the next stage.

Be very aggressive and definitely expand your hand range..

Mawoyto, when he is on the button on stage 0, it won't be checked to him, he's first to act. That said, I agree with the rest of the statement

Heads up is a weird game, but a very good skill to develop. Raise your buttons or fold, never limp in the button. And pay attention to how deep stacks are. If stacks are deep, you can afford to see more flops, especially if you're better than your opponent.

Also, avoid calling all in pre- unless they are either really short stacked or you have a monster. Calling an all in is different than raising all in.

Way too timid. Need to open up play.

Guys, thank you so much for the advice. Everyone seems to be saying about the same thing and it makes a lot of sense.
Plenty of basic, basic adjustments to make, particularly in stages 0,1,3. This was all really helpful.
I downloaded an odds chart for heads up prefold and I'll just keep it handy until I can force myself to start overcoming my total passivity.

I really appreciate all the friendly replies.

Also: "She"