I'm trying to go for a no-hit run, hoping to get a pb of 7:30-8:00 but i can't get 8-1 and 8-2 right... are there any tips i can use to try and get through? I'll post images to where i'm having trouble with here: 
(8-1) and 
(8-2)
Like xDrHellx said, git gud.
(you'd probably be better off asking in the game's forum https://www.speedrun.com/smb1 )
The level is always the same in that game, right? Try changing how you approach practicing. Instead of trusting your reactions, focus on the timing of your inputs. The idea is to make the timing muscle memory so you don't get overwhelmed when you hit that area. When you practice the difficult parts of those levels, consciously focus on exactly how long you hold the jump or forward button, then modify it until it is consistently what you expect. If you do it right, you shouldn't even have to look at the screen to get it right; your muscle memory will remember to hold this button for a beat and a half, then hit this combo, and you don't even have to think about it. If you practice it enough (correctly), you can make the most difficult parts the easiest.
[quote] The level is always the same in that game, right? [/quote]
Not exactly. There's global cycles from power-on. That's why if you ever watch truly elite runners of the game like darbian or kosmic grind out runs they have to put a very specific negative offset on their timer to know they're on the right cycle. I don't remember the exact numbers but I just remember that when darbian started going for two flagpole glitches he had to change it (and presumably will again if he ever does runs with 2 FPG's and fast 4-2).
This is even more apparent in Lost Levels (which has pretty much all the same concepts as SMB1 aside from the different run and jump physics Mario and Luigi have). As that game is harder and hasn't been optimized down to every frame the way SMB1 has, you'll occasionally see them purposely lose time on one stage (never more than .3s) so as to be on the cycle they're familiar with in the next one.
You'd have better luck with this kind of post in the respective game forums and community discussion areas, like their Discord. Thanks.