وبعضها

In a sentence

• الأشجار كانت جميلة، وبعضها كان مزهراً.

  The trees were beautiful, and some of them were blooming.

  The word "وبعضها" is used here to refer to a specific subset of a previously mentioned group (the trees), appending new information about this subset.

• اقترحت عليهم أفكاراً، وبعضها كان جديداً تماماً.

  I suggested ideas to them, and some of them were completely new.

  In this sentence, "وبعضها" points to certain ideas within a general set of mentioned ideas, marking a distinction of novelty for these specific ones.

• قرأت عدة كتب، وبعضها كان ممتعاً للغاية.

  I read several books, and some of them were highly enjoyable.

  Here, the term "وبعضها" indicates a select portion of the books described, adding qualitative description of those specific books.