Ok so I really dont understand how to calculate the experience a party aquires. So here is the set... please help. I am new here and will put some info about me in the bottom...

The PCs are two lvl 1 characters. They were captured and forced to fight in an arena (easy way to start the campaign off with some action). They had to fight 3 waves of enemies. Only one wave at the time but no chance to heal properly, replenish ammo or anything like that in between. The three waves were...

1. One gobling. CR: 1/2
2. Three kobolts. CR: 1/3 each..
3. A gladiator I basically copied from "Fighter sample lvl 1" from PH. I downgraded it some though cause they were gonna get slaughtered! (Nerfed his speed to 15 even if it was of medium size, lowered damage and AC midely).

So to begin with is this one encounter (since they had barely any time to breathe between round) or 3 (since they fought each battle separately)? Please help me calculate all the xp they get each! They also recieved no treassures what so ever for this (they only earned their freedom) so probably gonna boost their xp some extra in the end..

To my understanding you get more XP if the encounter in general had difficult pre-conditions. Such if you slay a kobolt that was almost strappted for you to kill you gain less XP than if you balance on a rope while protecting a princess that wants to die and you slay an evil kobolt! In this case it was pretty straight forward though! They were only required to make a fatigue check (due to no food or water for several days in prison before the gladiator arena). One played failed and suffered -1 on almost all checks and dmg. The other one had endurance and thus was immune to fatigue..

About me: I played some dnd back in the days (like 10 years ago) very unseriously. While I am more mature now and got more mature friends we've started to make our boardgaming evenings to dnd evenings. Is great fun! But I am not the best DM; consider myself a beginnerm, though quite familiar with playing a PC. Many rules slip out of my mind while we play and checking them up takes so long time when you just want to make a simple action and keep the fight going.

Thanks in advance! All people who voluntarily share information here should be of any good alignment!