pandas

df['sentences'] = df['content'].str.split(pattern2)
df['normal_text'] = df['sentences'].apply(lambda x: [re.sub(pattern3, ' ', sentence) for sentence in x])

polars

df = df.with_columns(pl.col('content').map_elements(lambda x: re.split(pattern2, x)).alias('sentences'))
df = df.with_columns(pl.col('sentences').map_elements(lambda x: [re.sub(pattern3, ' ', sentence) for sentence in x]).alias('normal_text'))

Amy more elegant way than this?