Hey guys thx for your posts.
Here is a little update : i decided to check out if the roots were risking crossing each other so i decided to experiment  taking out the seedling that has the seed stuck on it and put it in a pot, and check the soil. I found that its roots had almost reached the nearest seedling to it. So i decided in emergency to take out the two other seedlings (to put them in pots) and leave only the most vigorous one in the ground.

 When it came to the nearest one to the vigorous seedling, i tried to insert the tool that i used to dig them up the farthest possible from the vigorous seedling to avoid harming its roots, that led to inserting it near the seedling i was trying to remove, and a portion of the main root was accidently cut and left in the soil (i hope it will recover, because this one is a struggler, it had its head stuck in the ground while sprouting and remained bending till it got cut up by itself, but it regerenated and now it has leaves growing émoticône.

Thank you Blue Palm and Miguel for you answers.
@ Miguel : Thank you for your compliments I too visited your beautiful country last year (Lisboa and Porto), one of the best destinations i have ever visited, and the people there are great. Concerning the type of soil, i don't know exactly, but i would say slightly acidic as i already have 2 citrus trees and 3 orange trees (all well established).

Hi all;
I live in Tunis, Tunisia, (Zone 10b)… (but in my mind we are in 13b lol). So I as you understood, I am trying to push the zones away, notably with mango and soursop planting  This thread will talk about my soursop experience, I will launch a second thread about my mango experience, so that may profit to future zone pushers (as I profited from the thread of Pancrazio with his mango experience in Italy).
So I got a soursop fruit from ivory coast last june, I planted some seeds on the ground, and 40 days later, some of them sprouted.

I built a wood structure to cover them (I will wrap it with 2 layers of plastic bubble film and one layer of anti frost cloth (with an air space of 3 cm between the layers).



I planted the seeds too close to each other, I am wondering would’nt they disturb each other? (the roots). My first priority is the optimal growth of the most vigorous seedling of them, My second priority, is to keep a second seedling as a backup under the same greenhouse in case one of them dies. Do you think I should let them as they are for now and wait some time (how much) before transplanting any of them? Or do you think they are too close and I risk to have crossed root systems which will be difficult to separate later? (in this case I will now transplant the three less vigorous seedlings no matter the risk for them as my first priority is the most vigorous seedling, especially knowing that one seedling is broken and beginning to sprout multiple leaves from its extremity and another seedling has the seed still stuck in the leaf place)

My name is youssef, from Tunisia, I have a garden with citrus, orange, mandarine, apple trees. I have recently planted mango trees and trying to grow a soursop seedling from seed (challenging but exciting).
Have a nice day