Is taking a legitimate/legal(a.k.a doesn't related to stealing) shortcuts or simple lifehacks a sin? For example if I am trying to complete a project in the internet and I'm using external tools to help or improve my project without using a lot of my time and effort.I asked this question because doing these things might be related to laziness which is a sin.
Hello, and welcome to CF.
I pray you are blessed by being here.
To answer your question, no, why would making legitimate use of any tool God has provided, through the intelligence, skill, or inspiration given to another, be a sin?
It's not a sin to cut through the public park to get to the other side instead of walking all the way around either.
This kind of thinking will have you convinced you are doing something right before God to whip yourself.
There are some legitimate ascetical practices that are good for disciplining the flesh, and spiritually beneficial. If you have such concerns, you might try fasting, UNDER GUIDANCE (it can be easy to become prideful doing it on your own). But using something that makes you more efficient isn't lazy, it's smart. As long as no one is getting hurt and no laws broken, etc.
It is good to be aware of potential sins and temptations, but it's possible to focus too much on it as well and confuse yourself, thinking you sin in something when you don't, and too much of that can lead you to spiritual despair, which is difficult to overcome.
Start by focusing on the obvious sins.
Peace to you.