Well the lifestealer doesn't seem to have much of a clue since slark isn't revealed by gem, sentries, dust or necromicon units (true sight) anymore since the last balance patch.
I've watched a bit of your game and I think there are two areas where you can make pretty fast progress. First of all, controls. I'm not sure what your settings are but it seems to me that your "Camera acceleration" and "Camera speed" settings are set way too high, I'm sure you'll benefit a lot from lowering them a little bit so that you feel a bit more in control of your camera since it's one of the main tools you have to gather a maximum of information around you and act accordingly. You went mid and were in a 1v1 situation, yet the camera most of the time was centered in such a manner that you wouldn't be able to see the enemy hero and the creeps were at the far edge of your field of vision. Generally, you want your camera to be positioned so that your hero is to the far edge of the field of view. This is where the camera was during this whole creepwave when you were playing that particular game:
The issue with this is that you are not gathering any useful information on the opposite hero's movements, and thus you react much slower.
This would be a better spot to have the camera centered on:
This way, you have vision on the two main objectives in the lane. The opposite hero, as well as the creepwave. You can last hit and deny effectively, while still being able to react to the opponents movements by retreating if needed or moving up to play agressively. There's also a huge area on your cliff around your creepwave's archer where you are free to move without too much hassle.
Think also a little bit more about your controls setup and how comfortable you really are with them. One easy trick is to have specific items that you buy often always on the same slot. Bottle for example is always in the bottom right slot for me (keybind "C") and Blink Dagger is always in the upper second slot (keybind "S").
So yeah my first advice would be to try to move the camera much more and try to always center it on your objectives and not always your hero. Do not hesitate to change the settings I mentioned until you feel very comfortable moving the camera around. It shouldn't feel like a burden or something that handicaps you. I know it is a bit difficult to do at the start, but the faster you get used to doing this, the better you will play.
Another advice I can give you and that helps a lot is to always make a habit of clicking the enemy hero when you arrive in the lane. That way you know which items he bought and how he is going to play during the first minutes of the game. He bought a shit ton of regen and no stats? punish him by going for more last hits. No regen at all? Try to harass him a little bit more.
Another simple trick is to slow the creeps at the start of game. You can stand in front of them to slow them a bit. That way, the first creepwaves meet much closer to your tower giving you a much needed advantage early on. Uphill advantage is pretty big in this game, you can often easily exchange hits that you wouldn't be able to in normal circumstance with a hero that is downhill (because of the miss chance when attacking uphill).
Finally, every two minutes, make a habit of checking the rune. Wards and teammates camping runes help but that doesn't mean you should be ignoring them if you have no vision. A good way to make sure you can grab a rune is to use your skills (for example power shot) to push the lane right before it spawns. For example, you can nuke the creepwave at around 1:40 to push the lane. That way, your opponent has to make the choice between sacrificing gold/xp from the creeps at his tower or giving up the rune to you.
The second area where you can make fast progress is game knowledge. This comes from playing a few games, talking to friends who play dota and watching a few streams. You want to be in a position where you know what's the strengths and weaknesses of the hero you are playing in the particular match up he is in. Sticking to one hero for the first few games can be a good idea, but once you are a bit more comfortable with the game you should try as many heroes as possible. In the case of Windranger, I've seen you miss a lot of last hits with your power shots on creepwaves since you weren't gauging the damage it would do correctly. This should come with a few games.
You'll noticed that these small advices focus almost exclusively on the laning phase. Winning the laning phase puts your team in a great spot for the rest of the game and this is the area where you need to focus your efforts. Team fight sense and to a lesser extent "gank" sense comes mainly with games.