How do you Cross or come back from Magical World

I have an issue i cant manage to see how you can cross to the magical world or if you manage too how could you come back from it.
Is there some spell who can help, methods, or tricks ?

Crossing into the Magic Realm is covered in Realms of Power:Magic. You can't start researching the spells to travel between them until you have been there and back again, so you need to find your own way first. Solomonic travel (in The Cradle & The Crescent) can travel to the Magic and Faerie realms easily.

Thank you for the insight now i understand more how it works !!

Alternatively, you can use ReVi20 Piercing the Faerie Veil (or the equivalent for Magical the magical realm) to cross regios, until you reach the level 10 which should a boundary with the Magical realm.
Not all regios are connected to the realm though.

In RoP: Magic, there is the spell See the Paths through the Void, which needs to be tailored for each Form depending on the association of a Regio. I do not know if Piercing the magical Veil works for all magical aura or should be replaced by See the Paths...

So I guess depending if you have the book or not, and how important it is for your story to have specific spells per Form or not, you can use either.

Also consider that gates might exist.
Both gates in a regio in the mundane realm that can lead to the magic realm and vice versa.
RoP:magic does state somewhere that such gates are rare and almost always guarded by powerful beings.

In my own saga the Magi have discovered a series of Regios on Mount Blanik in Bohemia that lead to an increasingly more intact pagan site dedicated to a wind god. The lower levels of the regio and the mundane mountain are home to powerful Bjornaer long since passed into final twillight. He now roams the mountain killing any (non-Bjornaer) who attempt to climb it. He can be sneaked past and he does not enter the top 2-3 levels of the regios. The level 10 regio leads to a vestige in the magic realm which can be reached by crossing the boundary. The level 10 regio and the vestige have arcane connections to each other easing travel between them. The vestige contains an intact ghostly site with pagan ghost repeating the same ritual over and over again. By studying the ghosts of the long dead pagan priests it is possible to discover the ritual of worship which opens a gateway on the top of the immpossibly high mountain in the level 10 regio. This gate then leads to the magic realm proper if you jump through the archway into the clouds surrounding the mountain. Leap of faith like thing.
Once the ritual is known it can be carried out in the level 10 regio opening the gate to the magic realm.

Through the gate one lands on a plateau surrounded by clouds with other plateaus visible for endless stretches in every direction. The archway is also present. Another ritual must be discovered to open the gate back, although the archway does serve as an arcane connection to the archway in the vestige. Thus two travels through the twillight void will bring you back to the level 10 regio. Also this side of the gate is home to several air elementals which are hostile/very playful.