VityaSchel

So I suppose I did a very stupid mistake somewhere in 4-6,
but I'm really tired to seek for it and just skipping 4 and
6 steps isn't help, if someone found what's wrong with my
code, pls write somewhere idk I want to sleep

You may use chain command blocks, stack all them together 
or use repeaters like me. Important thing to remember is that
they must be executed followed by each other like here.
0. Create objectives with dummy or trigger type (this way
these objectives won't be affected by game events and can

VityaSchel

so I had to find a way to control ender dragon and every time it was flying away very fast but I found that with minecart it doesn't move but minecart cannot be invisible in any way so there is two command how to imitate minecart with ender dragon passanger

1. pick any two tags (ex. dragon, stand)

2. both have to be in cycled repetiteve command blocks

in this first command stand moving away to 0.001 block every tick
execute at @e[tag=stand] run tp @e[tag=stand] ~ ~ ~0.001 0 0

in second it teleports dragon to it every tick