I apologize in advance for the length, but I think it's important
I will be blunt to start, but I'll tell you some tips afterwards to try and make up for it (don't worry... I already feel bad).
This deck will lose a lot in the tournament. (now I'll explain why while also trying to be helpful as best I can)
Modern is a very vicious format where there's a certain set of cards you "have to"(in theory) have in order to win. These cards are also outrageously expensive. It's called a "Turn-6 Format" because that's the point you should be able to win at consistently.
Some of these cards are:
and the list goes on and on.
That being said, here are some basic things you can do with your deck to make it a little better:
Choose a "win condition". There's no point in building a deck if you don't know how it will win, so this is the first step towards making any deck. Do you want to be aggro, combo, or control? Once you accomplish that, go to the next step:
Get multiples of cards. This is what I tell every new player because it's not as obvious as it seems to more advanced players. You have a lot of "one ofs" in your deck, which is good sometimes but leads to a big problem: if I kill your [[Fiendslayer Paladin]], what then? Obviously you have your Titan, but there's still no guarantee you'll draw it in time. You want multiples in order to keep your deck consistent. Finally:
Cut any cards that don't help you win. Nothing is worse than an opponent coming back from 1 life because you couldn't find one more burn spell, but instead drew a creature with defender.
Long story short: use the tournament as a learning experience to start building your decks better. See what worked in your deck, what could have worked better, whatever.
Learn what you should have 1, 2, 3, or 4 of in your deck, learn what lands you need, and make sure they all help you win ASAP. This is 200x more important than winning with a $150 card because people say it's good. I really hoped this helped :)