[Map✓] Help for map connexion & script creation

Hello !
I introduce myself :
I like pokemon , but I LOVE pokemon gold , silver and crystal.
I played like 3 years on my old gameboy color.
Then , I discovered romhacking !
I played almost every 2nd gen rom hack, my favourite was Pokemon Prism and Bronze 2 for sure !
And now , I want to create my own rom hack , with new region and new story !
But , you know , i'm just a little kid , I can't learn all by my own ... And romhacking of pokemon silver or gold is not very popular...
So I need some help please :p
I already know some things , like editing map , create or edit warp .
But , for map connexion ... dude that's so hard for me ! Sometimes , if I make a city bigger , in the editor everything is good , but in-game the road connected to the city start INSIDE the city.
It's just a corruption ?
And if I wan't to modify , idk how it work...
I'm gonna add screenshot because my english is bad and it's hard to explain bruh
And btw I don't know how to create event , create script or edit script and add it to my rom...
Please , I need help :)
My tools :
Create text : pksv
Map editing : johtomap
Market editing : MartEd
Edit text : PokeText
Create / edit trainer : OneGSCTrainer
Create / edit pokemon in the grass : GSC Wild Pokemon Editor
Thanks :)
Screenshot : the red part teleport to the black part...