Heavy
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of heavy? It's also heavy.
おもい
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
You're lifting something that's really heavy. Oof! You lift it above your head. You're so awesome. You scream: "OH! MORE!" (おも) they put more. You yell it again: "OH, MORE!" and again: "OH, MORE!" Go ahead and act this out wherever you are, pretending like you're holding a couch or two or three over your head, saying "OH MORE!"
そのにもつは重そうですね。
That luggage looks heavy.
この車、重すぎてうでがもげそう。
This car is so heavy that my arm is about to fall off.
「足を踏んでしまってごめんなさい。」「ちょっと重かったけど、どうってことないよ。」
"I’m sorry I stepped on your foot." "No problem. It was a little heavy, but no harm done."