I am writing a briefing paper, and it only consists of facts and citations I am writing a briefing paper, and it only consists of facts and citations. Literally every sentence is a quote or a link to another source. 

The topic of the paper is pretty much covered and there are no problems with a structure of it (my supervisor told that). The problem is that it is too dry.

How do I add my own comments to it? 

I struggle expressing my own thoughts and I do not have an experience with writing. I do not feel like I am qualified to comment on such topics, in some way I feel like adding my own point of view is not right, as everyone should make their own conclusions from the given information. Am I wrong?
Even if all that you are doing is summarizing pre-existing material, if you aren't writing in your own words, you are likely to produce terrible prose.

In summarization, you are necessarily making decisions about what to include and what to omit. You have reasons for making those decisions. That is your perspective on the material.

A good briefing can be quite exciting and compelling, even if it is filled to the brim with citations.  Too many quotations however, is likely to be a problem, because those quotations are taken from a different context and will not flow together to make a narrative.

If you are having trouble breaking away from these prior words, I might suggest the following radical technique: having first made you collection of material as you have described, open a fresh, blank, document, and starting writing without looking at any of the original material.  In this circumstance, your memory will be not good enough to continue using only the words of others, and you may be better able to start developing your own expression and perspective on the material.