this app is good but I need help
Read up on basic grammatical components and tenses on the internet. It's beneficial to know what the subject, object, verb, etc. of the sentences are, and to be able to distinguish between present, past, and future tenses, etc. You'd be surprised to find that English has 12 tenses! (that you already know!) I recommend englishpage.com for you to get acquainted with your own English tenses first.
Try conjuguemos.com for verb conjugations, and news sites like elmundo.es for reading. Really, just google "Spanish learning resources" and you'll find a wealth of information. For grammar help, try YouTube videos. I've found them to be excellent at explaining all the kinks and vagaries that Duolingo doesn't teach.
Try to use Spanish as soon as possible! It's okay if you sound like a babbling baby, you must embarrass yourself to improve your Spanish! Besides, more often than not, native speakers will appreciate your effort. Interpals.net is a great resource for meeting native speakers.