I started mountaineering at the end of last year and I really like it.
I went hiking in the mountains for the first time at the end of last year, and now I'm a big fan.
英語で言う場合、登山を昨年末から始めた、という文を先に言った方が自然な文になります。
ーI started mountaineering at the end of last year and I really like it.
「昨年末に登山を始めて（登山が）とても気に入っています」
ーI went hiking in the mountains for the first time at the end of last year, and now I'm a big fan.
「昨年末初めて登山をして、すごく（登山の）ファンになりました」
ご参考まで！
カナダ 
