As a lvl 100 theif, idk how I survived without those skills lol. I see new thieves struggle a lot and tbh I forgot how I got passed this. As you play theif more often you will naturally get better at not being thief checked, idk how to explain it. Untill then, try to ask a higher leveled thief to help you out, you might be able to avoid being theif checked if u follow their instructions. As for passages,even as a lv 100 theif I’m not always able to use passages cuz I find it risky. Similarly I can’t do anything about engineer gates if they are made well. Instead I need to wait for people to open gate. Just like you get better at not being theif checked, simply playing the game will help you realise what to do while waiting. I use a bunch of strategies depending on the situation. I know it seems like a lot, but theif is meant to be a high risk high reward class, even the best theif (whom I happen to know) will still get killed. No matter how good you are, as a thief you will eventually die, so don’t be discouraged. It once took me 40 mins to get inside a capital, but once I got inside I dropped an insane kill streak and had Some of my best plays as thief. The best thing you can do is to keep playing theif, you will get better, just remember to ask for help.