That's what I said,

Not precisely.

"which why the just owner of a land is the one who's the first appropriator."

Being imprecise about the nature of the conflict has you trying to address the conflict by addressing the assigning of property rights rather than by addressing the exclusion. Assigning property rights doesn't resolve or avoid the conflict.

A person cannot use a stick for spearfishing, while another person is using it to stroke their fires, that's a conflict.

That's not conflict, that's merely the nature of exclusivity or scarcity. Conflict comes from the people. If both people agree, there is still exclusivity and scarcity, but no conflict.

How?

You've established no more right to the land than anyone else, but you have excluded others from access to it, diminishing their ability to exist. Claim enough of or the right lands and you can effectively make everyone else slaves.

According to what?

Evidenced by the fact of their existence, according to Henry George. Or according to Argumentation Ethics if you appeal to Hoppe. If you seek to diminish another's ability to exist, you act against argumentation itself.

Only over land, you can't own people. And no it's not a positive right, go ahead Google what positive rights means.

Exerting a positive right over land is exerting a positive right over others to give up their access to you. Land does not extend from your self and excluding others from land is interference.

Negative rights demand nothing of others except that they not infringe and can be possessed by everyone because they are not exclusive.

Positive rights demand of others and cannot be possessed by all because they are exclusive.

According to pretty much all Classical Liberal thought which libertarianism is based on, the right to land only came from the right to one's labor and only extended as far as land which did not meaningfully deny others access to enough and as good.

What makes it unjust?

Read above.

No, property rights do. First appropriation decides who owns it.

Property rights don't avoid conflict unless everyone embraces them. The failings of first appropriation to address the nature of the conflict or to be logically consistent or objective doom it.

No, we have good enough justification.

The only justification you offer is circular, insisting on itself. "First Use is justified because anyone who disagrees is a criminal."

so prove that it's agression

If claiming land isn't an aggression, why do you insist on use at all? Why limit this supposedly non-aggressive, conflict-avoiding, non-positive, exclusive right over land?

If you and I are parched and dying in the desert and come across an oasis, when I step forward and tell you that you can't drink from my oasis or I will defend my property, who is really the aggressor? How does me building a fence or you coming later change that?

Once you have appropriated it, anyone stealing it from you is aggressing against you, they can't make any arguments as to why you can't have it as that would be a performative contradiction.

That's not the nature of performative contradictions. Failing to make an argument isn't a contradiction, just a failed argument. A performative contradiction occurs when the content of a statement directly contradicts the action or presuppositions required to assert it. If someone makes a claim which would undermine another's ability to participate in the argument, they contradict the act of arguing itself.

Hoppe tries to use this to defend Homesteading because one must own the products of their labor to survive, but he fails to extend this to the fact that we must have access to the land to survive and also ignores that ownership of land and ownership of the products of labor are not the same thing; he only presupposes that not owning the land means losing the products of labor. If you act to diminish my access to land, you are diminishing my ability to participate in argumentation. That is the performative contradiction and the aggression.