Note: I mainly give negative feedback. Don't feel discouraged from making maps after reading my feedback.
The first and biggest issue is that this map would serve as a perfect medium map if it were not for the roofed jumps in the middle. There are two main problems with this. One, it is slightly unfair for people first playing the map that there are invisible blocks that serve as the roofs. It can be quite confusing and might take people some time to figure it out. (Especially to people who don't know about barriers blocks, but these people aren't very common) Two, it doesn't make for a very balanced map if there is one primary source of difficulty that stretches a map to a higher difficulty. Most of the other jumps are medium difficulty, but the roofed section stretches the map's difficulty so much it breaks the threshold for medium and flows into hard. This is why it's unbalanced; The rest of the map is simple while the roofed section is the only problem.
Another problem is that the only jumps in this map are block jumps. (Save for the roofed jumps, which are just a type of block jump) It makes a map kind of stale and boring to play. I would recommend making some of the block jumps block/ladder jumps, where you jump to a ladder on the side of a block.
The end section of the map is ever so slightly confusing in which you have to go down with the barriers in the way. I would recommend making it so that you fall straight down, and the end of the map is at the side of the hourglass so there's no cheating allowed. Then, there's parkour around the hourglass to reach the finish. However, the design of the hourglass doesn't allow much for that kind of thing, and people might be able to cheat still.
The hourglass base is not a perfect circle. I use this circle chart when making circles. The number under each circle is the diameter.
http://i.imgur.com/LtAQ3Is.jpg
This hourglass has a diameter of 23, so you build the circle that's labelled 23. However, this would require a full re-designing of the hourglass.
Around the hourglass, the jumps are in straight lines, forming a kind of square. It looks kind of out of place and choppy. It would be nice if the jumps were in some sort of curve around the hourglass for some conformity and flow.
The sand at the bottom of the hourglass is unrealistic. Sand falls to the center and creates a mound in real life, but the formation of sand in the bottom of your hourglass has little mounds all around the edge. I can't imagine a scenario in which you can cause sand in an hourglass to make that formation.
It peeves me a little that the map name is "Time is slowing down" when there is nothing to suggest that time is slowing down. There is only an hourglass to suggest that the map is time-related, but even then, time alone is time and does not relate to the slowing of itself. I suggest just changing the name of the map to "Hourglass PK."