hello i'm currently roleplaying sorcere and i love it but was wondering since i can drop spell and replace them how does the system works , do i have a set of known spell and i can have them all from 2 lvl and non of 1st lvl is that possible ?

Hello Damnos.

1. Since I can drop spells and replace them, how does the system work?  See the section "Spells Known of 1st Level and Higher" under the Sorcerer entry.
2. Do I have a set of known spells?  Yes.  You choose which spells to know.  The number of spells you may know is listed in the Sorcerer Table under "Spells Known".
3. I can have all from 2nd lvl and non of 1st lvl. Is that possible?  Yes, this is possible, but it takes several levels to accomplish.  For example:
   
   • Character level 2:  1st level spells known = 3.
   • Character level 3:  Learn a 2nd level spell and switch a 1st level spell to a 2nd level spell.  1st level spells known = 2.  2nd level spells known = 2.
   • Character level 4:  Learn a 2nd level spell and switch a 1st level spell to a 2nd level spell.  1st level spells known = 1.  2nd level spells known = 4.
   • Character level 5:  Learn a 2nd level spell and switch a 1st level spell to a 2nd level spell.  1st level spells known = 0.  2nd level spells known = 6.

thank you a lot jesse from i understand i can change the list of known spell one by one i can't do it all at once when i lvl up :) 

Quote from Damnos >>

thank you a lot jesse from i understand i can change the list of known spell one by one i can't do it all at once when i lvl up :) 

 That's correct.  You may change one known spell when you level up.

Sorcerer magic is slightly (but distinctly) different in nature than other caster classes. Sorcerers' spells known are literally spells known. They don't learn spells like Wizards/Arcane Tricksters/Eldritch Knights through study and transcription into a spellbook, nor are they granted their known spells by an outside source (Cleric domain deities, Druid circles, Warlock patrons). Sorcerers have powerful magic through their bloodlines. They are naturally gifted with the ability to harness The Weave to produce magical effects. The spells they know are akin to an instinctual understanding of spellcraft, and are transient by nature. 

When you choose to "replace" one spell known with another, you can think about it as a "use it or lose it" type of situation. Your mental capacity for remembering how to produce a specific magical effect is limited. If you start focusing on mastering new magical effects, you gradually start forgetting the one(s) you aren't focusing on anymore. You forget that one key gesture or incantation you needed to produce that specific effect.

Good way to think about it.  I like that description.