Hey Halutza!
Malphite main here :) It makes me really happy to see people playing someone who is arguably my favorite champ in the game right now.
I tend to take Mal a different route than most players, but he works for me. Mana is going to be your biggest challenge early on, so you'll have to be conscious of what you're using, and how much Mana you have left.
Mal's Q is his best early level skill, and honestly my favorite for both starting and ending fights. Depending on the enemy team composition, he can put enough pressure on the top laner (and draw the Jungler up there) to actually cripple the game entirely.
I wrote up a guide on how I play him a little wihle ago, which I'll link HERE if you want to check it out. Results may vary, and a skilled opponent can outduel you early if you make the mistake of engaging for an all-in before level 3.
Best advice I can give is to always farm--kill the minions for gold, take care of your turret, and see if you can get someone who can capitalize on your ult's knock-up to back you up later in the game.
(Somehow managed to get a Yasuo 38 kills with our Ults working together).
Feel free to add me in game if you want to play or talk a little more about the champ.