There are 2 ways to climb, one being grabbing on a wall and swinging back and forth gaining enough momentum to swing your arm slightly above the other one, and just repeat that process. The other slightly more difficult skill is climbing, while climbing will allow you to climb infinitely in height, it isn't too efficient, it's mainly used if you are just barely too low on a ledge to climb on top of a platform. The first and easier skill being strafe jumping, this is just a super quick way to move and allows you to jump ridiculously far, meaning you can end up skipping a lot of parts of level, in order to do this, you really just need to move diagonally while holding the jump button and having your arms out. With that being said, there were 2 skills that seriously help speed things up and that I would recommend you learn, even if you aren't achievement hunting. A big issue with this game that I found was that I had almost every single achievement for every level except for probably 1 or 2 per level, and it was always achievements that you had to do right at the end of the level.
With that being said, even if you didn't have every achievement known and ready to do in order, this normally would probably only take somewhere around 20 hours, I already had loads of playtime on this game before I actually started achievement hunting. While this took me over 30 hours, you could definitely beat this game in probably less than 10 if you did every single achievement as you did every level in order. The reason this game took so long to beat, was that this game has over 100 achievements, with each level having probably around 5-10 on average, some with more, some with less. Unlike most games, when it comes to achievements, I cannot recall a single difficult achievement that really put a dent in my progress at all. 38h ProgressThis game is one of the easiest games too 100% that I've ever played, with that being said, it was also one of the most time-consuming games to 100%.