Shattered my ankle last year. I used a kneeling scooter, but I commuted by car. Had no problem using crutches in my 20s. Now, in my 50s, I found them exhausting.
A lot of people recommend going up/down stairs on your butt. Sure eliminates the possibility of falling. Easier going down as you stop a stair or 2 before the end and stand up. Going up, you end up at the top and need to stand from the floor. May be easier to turn over to your knees and stand from there.
Using the crutches for stairs requires some practice. What worked for me was:
-going up - keep crutches on stair where your foot is, bracing on crutches, hop up onto next step, bring crutches up, and repeat. Basically the opposite of what you were trying.
-going down - put crutches on stair below you, make sure they are solid, and slide your foot down.
When I looked on-line, I saw people recommending both possible orders for up and down - which is why I specified that this is what worked for me.
If there is a solid handrail, rely heavily on that and use both crutches in your offhand.
Make sure your crutches are the correct height. Many people have them too tall, and rest their armpits on the pads.
Consider looking into a shower chair. You may not be able to get your cast wet, so if you have a tub, you might just try baths with your leg hanging over the edge. Getting over your shower step is no big deal. Position crutches inside shower, swing forward into shower, put crutches outside, lean against the wall while showering. When exiting, reverse, making sure the crutches are dry and stable.
Good luck.