Devil Daggers

Survive for 500 seconds (8 mins 20 seconds.)

There's no easy way to get this. Keep playing. Memorize the waves. Build a strategy. Practice your aim and get good. Getting the achievement may take anywhere from dozens to hundreds of hours. Be ready to put in the work, and good luck. When you hit a wall or get stuck watch some of the top replays and follow very closely what they do around the part you're stuck at. Just watching 1 or 2 replays when you're at a wall will really help give you some ideas and up your gameplay.

Here is my winning run of 522s which took around 122 hours on Steam.

There are some mechanics and strategies to learn such as upgrades, homing daggers, shotgun technique and farming. Here is a very comprehensive steam guide that should teach you everything you need to know.
https://steamcommunity.com/sharedfiles/filedetails/?id=1248222759

There are also many YouTube guides that will help put you in the right direction when practicing.

Survive for 500 seconds (8 mins 20 seconds.)

There's no easy way to get this. Keep playing. Memorize the waves. Build a strategy. Practice your aim and get good. Getting the achievement may take anywhere from dozens to hundreds of hours. Be ready to put in the work, and good luck.

Here's an example of a 500+ second run by SoulAdor with 90 hours playtime on Steam.

There are some hidden mechanics and strategies to learn such as upgrades, homing daggers and farming. Here is a very comprehensive guide steam guide that should teach you everything you need to know.
https://steamcommunity.com/sharedfiles/filedetails/?id=1248222759

There are also many YouTube guides that will help put you in the right direction when practicing.

Survive for 500 seconds (8 mins 20 seconds.)

There's no easy way to get this. Keep playing. Memorize the waves. Build a strategy. Practice your aim and get good. Getting the achievement may take anywhere from dozens to hundreds of hours. Be ready to put in the work, and good luck.

Here's an example of a 500+ second run by SoulAdor with 90 hours playtime on Steam.
https://www.youtube.com/watch?v=tgyhT5xmN8E

There are some hidden mechanics and strategies to learn such as upgrades, homing daggers and farming. Here is a very comprehensive guide steam guide that should teach you everything you need to know.
https://steamcommunity.com/sharedfiles/filedetails/?id=1248222759

There are also many YouTube guides that will help put you in the right direction when practicing.
https://www.youtube.com/watch?v=B0YLXbiGt70