Hello.
So the very first thing is to fix your mana base. Your deck uses needs more Black mana than White mana, yet White is the color produced the most. You want the two pie charts to be as close as possible.
Now, your run 71 cards, many of them being single copies. This creates the problem of your deck not being consistent. Being defensive is pretty vague, and due to the number of cards and the fact that many are only a single copy, there is no reliable general strategy with each game, but one that has to be made up on the spot, more than other decks will. This is also an issue that an opponent will have there own deck doing its own thing, which will not wait for a deck to get all of its pieces in place. Math is a major part of this game, and it needs to be taken into account. Also, due to the deck size, the current land base doesn't fit. The roughly 20 lands idea only really works with a 60 card deck, and as yours is 71, you have a good chance of not getting enough land during a game.
Sorry if this sounds aggressive or mean, but Math is very important in Magic. By no means should you take my words as a personal attack, but as a means to improve. Everyone started off somewhere, and nobody is perfect at the game. Good luck.