I’m sorry this is so frustrating for you, I think it’s often made very complex (especially with sourdough).
My dad was a baker, so I grew up making vast quantities of the stuff! As a result I am very lazy and slapdash about it, but here is what I do.
Buy good flour. It must be strong, and unless you want very dense bread, at least half white. If you want wholemeal start with half and half white and wholemeal and up the wholemeal gradually until you get the texture and taste you like. Full wholemeal is too dense for many people. I buy mine from Wessex Mill (who are partially open for orders atm) and handily sell half and half, and have had reasonable results with Waitrose’s, but rubbish results with doves farm.
Don’t put sugar in it.
Don’t rush it.
Don’t keep it too warm.
Eat it the day you make it, or freeze it. It really doesn’t keep.
I make mine in the bread maker every Friday, on the pizza dough setting, which takes 45 minutes. This is a fast mix, bit of a rest, bashing good knead, first rise for half an hour or so and then I take it out for a squash-and-shape. I often end up doing squash and shape twice because I am not ready when it is. I usually shape into rolls and and then I put it the fridge all night. Yes, really.
When I get up on Saturday morning. Or perhaps after lunch. Or sometimes even when we get in from somewhere on Saturday night, I fling it straight into a hot oven for fifteen minutes. Then I put them in the freezer and nuke them for one minute when I want one.
I think the problem with your bread is a firstly sugar. Even a little makes bread denser. I know it’s counter-intuitive, but my bread became much fluffier without it, instantly, when I stopped adding it on the miller’s recommendation. Secondly, I think you are proving it much too warm. Again, contrary to popular belief, you don’t need a warm place to prove bread. It will prove faster in a warm place, but this isn’t a good thing. Firstly, you get fewer, bigger air pockets, which make denser bread (you want a lot of little ones) and secondly (and I think this is your main issue) as the air bubbles produced by the yeast get bigger, the dough around it gets thinner (think ballon). So when it’s baked it can’t support the bubble and collapses. I think this is what is happening to your bread. Sugar makes this worse, because it makes the yeast act faster.
You can prove bread in a warm place, but it takes more skill to find the sweet spot between enough rising so there is air, and too much when it collapses. In a very warm place it can be just a couple of minutes and vary enormously between houses, summer and winter. In the fridge, it’ll be hours and hours and pretty constant. Hence my lazy Saturday mornings.
It is possible that your flour is a bit duff (this varies year to year, Miller to miller, wheat to wheat and so on) or that your yeast is a bit duff (but it’s much tougher than most people think) so start with flour. It’s also possible that you are not kneading enough (kneading creates strength in the bread) or that your dough is too wet (which means it can’t hold its structure well. If it sticks to you a lot, it’s too wet) or too dry (when it would be too stiff to rise. It should be soft, and make you want sink your fingers into it, and it should stick a little). I don’t think it’s salt. Salt does indeed impede yeast action, but you are getting rise and then a sink, so your yeast is working.
My recipe for good measure
400g Wessex Mill Strong White Bread Flour (or 200g White, 200g wholemeal)
1 tsp of salt
A slosh of olive oil (About two tablespoons. Amount not crucial. Or any type of oil. Or a chunk of butter. Whatever)
A dessert spoon of yeast (I keep a measure in the yeast jar and thought it was a tablespoon for years!)
240ml of water
Mix it all together, until it makes a soft dough. Then knead it. It should feel ‘nice’ - pliable and squishy, but not too sticky. Softer than playdoh or biscuit dough and sort of springy. Leave it around in the kitchen covered with a tea towel for half an hour or so. It should look puffy and floofy. (Don’t worry about ‘doubling’ that’s crazy hard to estimate in a bowl!) Give it a quick squish around to make it like it was before, then put it into its tin, or shape into rolls (eight is a good size for this mix) or a round (whatever. My kid makes dolphins and plaits and alsorts) on a baking tray, cover with a tea towel and leave in the fridge overnight.
In the morning, get the oven up to 180°C (or 200 for a non fan, maybe. It’s not critical, but don’t put it into a cold oven) take off the tea towel and bake for fifteen minutes for rolls (I don’t know how long a loaf would take, I haven't made one for years. I can certainly try, if you’d like). When they start to brown, take them out and tap the bottom. It should feel dry and sound slightly hollow)
Eat it that day, it won’t keep overnight (it will be ok for toast, but it’s so good when you first make it you won’t want to eat day old bread anymore. Shape and bake it in quantities that you eat it in, or freeze it in slices if you really like slices. It’s better frozen as rolls though. They are quite soft enough for sandwiches and lovely with soup.
I would not be adverse to doing a video, for people who really like visual learning, if people think it would help? It looks an awful lot written down!
I’m not qualified to comment on sourdough. I made it once, and it took days and days of faffing around feeding starters and halving the mix and waiting and so on, and the bread was EXACTLY the same at the stuff I had been making in 45 minutes every Friday for years. So I didn’t bother again. I concluded that the reason people like sourdough is that bread needs time to develop flavour. Mine already had it, so it wasn’t any better.
