inexperienced; unfamiliar (with); unversed; lacking experience
不慣れなもので、すみません。
I apologize, as I'm still unfamiliar with this.
電車の乗り換えに不慣れで戸惑った。
I was confused because I'm unfamiliar with train transfers.
不慣れな仕事なので、時間がかかってしまう。
Since it's unfamiliar work, it takes me a lot of time.