Essam - Locky Law has rightly asked, "What is it that you want to analyse in the comments"? First, you must look for a theme or related themes that is worth analyzing Facebook comments for research purposes. You need to be cautious that most of the comments uploaded on Facebook may not be relevant from research point of view. Select Page Data to download key engagement metrics for your page. Choose the data type, range, file format, and layout for your Facebook Insights data. You can use thematic content analysis as a research technique for the purpose of qualitative research. You can pick up themes are patterns across data sets that are important to the description of a phenomenon and are associated with your specific research question. Familiarize yourself with the data and assign preliminary codes to your data in order to describe the content. Search for patterns or themes in your codes across the different Facebook comments. Define and review themes and finally write your report.
When you identify the theme(s) of your qualitative research, you can analyse the text / content. There are various software that can be used for textual analysis, including MAXQDA, NVIVO, ATLAS, etc.
Check this out: Woods, M., Paulus, T., Atkins, D. P., & Macklin, R. (2016). Advancing qualitative research using qualitative data analysis software (QDAS)? Reviewing potential versus practice in published studies using ATLAS. ti and NVivo, 1994–2013. Social Science Computer Review, 34(5), 597-617.
Essam Al-Sibahee , still not clear. Are you going to perform linguistic analysis or multimodal analysis? What kind of doctors use Facebook comments to talk about medical conditions? If they really do, with whom do they talk to? How credible are these comments? Are these comments made by real doctors? How can you confirm their identity?
You might find this work by Braun and Clarke useful, it's a step by step guide on how to do reliable thematic analysis, it helped me a lot with my qualitative analysis https://core.ac.uk/download/pdf/1347976.pdf
Locky Law It is a Facebook group (secret) in which doctors discuss medical conditions (Similar to MedShare or Fig.1). The group is only for doctors and no one joins it unless he\she shows the medical credentials.
Essam Al-Sibahee Theme analysis seems to be one of the many ways for you. You may have a look at this: Article Effective Healthcare Worker-Patient Communication in Hong Ko...