Abstractive Opinion Summarization with different level of sentiment

My name is Bhargav, I have a dataset that consists of different levels (-1 to +1 with intervals of 0.2) of opinions in the form of text from several users on a specific topic collected from one of the discussion boards. Now I would like to summarize the opinions of all users at each level using an abstractive summarization technique. I am new to the field of NLP. Please suggest a starting point and sample models to perform the task.
Thanks in advance.