Not much advice I can offer on these. I recommend beating the Lost Island time trials first. Doing this unlocks the Golden Shotgun, the golden shotgun pretty much kills everything in the game with one hit, this will save you a lot of time as fights won't last more than two seconds. The Lost Island time trials are the easiest time trials in my opinion so they shouldn't give you too much trouble. You will be able to enable the golden shotgun in the cheat menu that is under options (don't worry cheats don't disable achievements). Practice is key, once you learn the layouts of the levels these achievements will not be very challenging.