回答
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I can't easily reach the ground with my feet on this bike/motorbike/motorcycle so I'm worried about injuring myself.
確かに特に初心者の場合には、足が地面まで届けないと危ないですよね。
(easily) reach the ground = (簡単に)地面まで達する・届く
怪我が心配 = I'm worried about injuring myself ; I'm worried about injuries