To who it may concern,
these guide is based on a 2v2 game with and vs unknown champions on the midlane of summoners rift. The pros and cons of this build are the following ones:
Pros: -Q does a lot of dmg and the slow is great for chasing
-W is a great AOE for farming minions
-if used right Mundo can have over 3000hp in midgame
-got an awesome lane sustain
-saves money because of the missing need of health potions in the mid-earlygame
-great bate against inexperienced summoners because of his ult
-no need of mana
-easy to learn
Cons: -ult can be countered by ingnite
-can be hard to hit q against experienced enemys
-no cc if enemy can dodge the Q

Q: your first ability (Infected Cleaver)
W: your second ability (Burning Agony)
E: your third ability (Masochism)
Ult: your special(ultimate) ability wich is bindet to the key r (Sadism)
Chasing: running behind an fleeing enemy with the goal to cach him
AOE: a ability doing damage in an area
Lane sustain: staying a long time at your lane and have the chance to farm a lot without needing any potions
Ingnite: a summoner spell wich cases a enemy champion in flames and does damage over time
cc: crowd control wich includes silences, slows, fears and stuns
Silence: some abilities lay a silence on an enemy champion, so he isn't able to use his abilities for a short time. You can see how long a champion is silenced if you look at the Small white bar under his healthbar
Slow: a slow lowers the movementspeed of a champion for a short amount of time. you can see if a champion is stunned if there is a trail of yellow triagles at the ground behind him.
Stun: a champion is unable to move and cast abilities and summoner spells for a short time
Fear: a champion is unable to be controlled for a short time. acts like a stun but the feared champion flees from the fearing champion.
Farm: killing minions with lasthits wich gives you money for each killed minion
Lasthit: doing the killing damage to a minion
AP: ability power. But not every ability does AP dmg" (is countered by magic resistance)
AD: attackdamage. The autoattacks scale on ad but also some abilities (is countered by armor)
Carry: one of the most important parts on a team. does his main damage with autoatacks. A good adc wins the whole game if he is fed.
Fed: if someone is fed, he got a lot of kills and is a higher level and got more items. A fed champion is hard to kill in a 1v1 if both players got the same experience

How to play Mundo:
1. farm with your q
2. don't use your w for farming in earlygame it costs to much health
3. make shure you use your passive for regaining health whenever you need it
4. spam your q in fights and use it for harassing in the laning phase
5. use your q for chasing
6. activate your ult whenever you are halflife it got only 60 sec cooldown

How to fight with Mundo:
1. start a fight with a Q
2. activate W and run straight to the enemy
3. activate e and do autoattacks at the enemy champion
4. cast your q whenever it's ready
5. activate your ult early enough (halflife or earlyer) so the enemy champion cant kill you because of the health it costs