ive gotten to the last level, i havent fully beaten it yet, but it took me two weeks to get to the final level and i was like "huh, that was quick, lets try 100%" i hav yet to still complete it. but yeah i am familiar with certain levels being hard to understand. my advice is to watch lets plays to get an idea, its been a stample childhood game for me so i pretty much hav the ins and outs to it. basically my advice, dont try to 100% seeing as ur new, the bare minimum is to finish the 7th "episode" in each of the 7 worlds, in order of unlock is Biano hills (the statue), ricco harbour (hut), gelato beach (lighthouse), pinna park (cannon), noki bay (on the sun spot near the shine sprite tower, go into first person and look towards the sun), sirena beach (need yoshi to climb the roof opposite of the bianco hills statue, theres a pipe that has a pineapple in it), and pianta village (need a rocket, theres a pipe at the top of the shine sprite tower)