ex-appliance tech here who has seen many DIY vents by homeowners and contractors almost start housefires due to improper venting.

Like for example, what material are you running through the walls? What state do you live in? In Massachusetts, it's against the law to run non-metal and non-rigid transition ducts through walls. How many 90-degree elbows do you have? How long is the actual venting? What is the airflow coming out of the vent? https://www.mass.gov/doc/780-cmr-7thed-65pdf/download

Your state or area may have specific laws you need to follow.

I've gotten in so many fights with homeowners trying to burn their houses down to save a couple of hundred bucks.

I saw in a comment that you're trying to prevent a 90-degree angle and you already have a long dryer vent. If your dryer vent is already longer than 20 feet and has 2 90-degree bends then you 100% need a professional as your airflow may not be strong enough and your vent will become unsafe very fast.

So I'm not really sure what the exact problem here is but it sounds like you are doing something unsafe which is why I'm going to finally say:

Just hire a professional.