new all over again

new to the forum and new to 40k again. i found a tyranid battle box unfinished from about 7 years ago and decided to try my hand at this one more time. i used to play eldar and did it rather well. now i'm toying with these tyranids and between the differences between them and eldar and all the new rules i'm getting slaughtered. i only play my 2 friends. one has a space marine army and he knows his stuff. the other plays orks and has over 3000 points painted and ready to roll. in our small games his army is different every time. i joined this forum cause i need help.