Although Koichi lost everything, he was able to gain a best friend in Viet.
It's not easy to obtain one's trust.
I got a lot out of my experience teaching English in Japan.
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means acquire so the verb vocab version is to acquire.
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 need to acquire an elephant (え) for your elephant collection. If you don't acquire an elephant, you'll look like an idiot in front of your elephant collecting friends.