How are your impressions looking? If you're getting high impressions, but low views, my guess is your CTR is pretty low.
Your thumbnails are very busy, and considering your channel has the word "lectures" in it, that tells me you're a study channel and to be real and blunt, your banner looks like you don't have much experience in design (and that's fair enough, not many people have a background in design) unfortunatly, you do need quality banners and thumbnails if you're going to come across as a professional channel, especially when it comes to lectures.
You have good titles, and your keywords look strong, but personally your thumbnails are weak, cluttered and very busy making the first impression of the video look like it's potentially a quickly put together video. That might not be the case, but lets be real, people judge a book on it's cover.
You've done the right job of using good titles and search times to get your videos in front of people. Without seeing the back end, my guess is your busy cluttered thumbnails are letting you down and people see your thumbnails and move past to find a video with a more crafted thumbnail that gives a better first impression.
Thumbnails are just as important as title and description. Look at your search impressions and if the impressions are there, that means your keyword research is working, but the views aren't that tells me you need to look at your thumbnails, not just the competition of the topic.