You’re not going to ruin them. Kids this age can test the patience of a saint especially when you are with them all day long.
I know you say you shout at them all the time, but I bet you don’t. I found my kids were delightful when they were playing in the bath, busy at the playground, “helping” in the kitchen eg laying the cutlery on the table, or snuggled up reading a book. Try and stop to notice when you are happy with them - and recognise it - “it makes me so happy when you play nicely, well done.”
When do you find them most annoying? Is it when you are rushing to get out, when they are bickering or throwing a tantrum, when they are messing around with their food, when they are disobeying your “perfectly reasonable” requests to stop playing and go to sleep?
Your view of how life should function and theirs will not coincide yet. Try to remember it’s not their fault. They don’t really understand that it’s not reasonable to take twenty minutes to put your shoes and coat on, or jump on the bed when you’re supposed to be lying on it.
Instead of getting cross make a game of it where you can - “I bet you you can’t find your shoes and get them on faster than me.”
Always set expectations - “we’ll do this for five more minutes - that’s about as long as a Peppa Pig cartoon, then it’s time to stop and get ready to leave.” Or “I’d like you to walk nicely together holding hands with me so then we can enjoy looking for birds while we walk to the park. Can you do that?”
Then it can be easier to remind them, “you promised to walk nicely with me. You’re trying to run off and that’s not allowed. If you can’t walk nicely we will have to go straight home. Lets try again.” And so on.
When you need them to settle down, warn them and then give them a countdown (54321) and then say firmly “that’s enough I asked you to stop” and step in to tell them off and make them say sorry mummy.
Ignore tantrums, they go away.
Don’t give in to whining or it never ends.
Don’t sweat the small stuff
Try to say yes as often as you can without ruining their health/sleep/screen limits
Of court this won’t work at first but if you do it calmly and firmly and diligently… most of the time … you’ll only want to scream into a pillow maximum twice a day.
Mine were both ok by age 5 and age 6 upwards is bliss until they are teens!