All of the people I work with who are senior to me are very nice.
All the people above me at my workplace are so nice to me.
ーAll of the people I work with who are senior to me are very nice.
「職場の先輩たちはみんなとても優しいです」
people I work with who are senior to me で「職場の先輩たち」と言えます。
ーAll the people above me at my workplace are so nice to me.
「職場の先輩たちはみんなとても優しいです」
people above me at my workplace でも「職場の先輩たち」と言えます。
ご参考まで！
カナダ 
