Assalamu alaikum. I understand where you're coming from as i was also born into a Muslim family but didnt start practising the deen until i was 25 (2 years ago). Alhamdulillah (all praise is due to Allah) that you know Islam is the truth and that you have emaan (faith), its a blessing. Dont worry about what everyone else is doing, we all have to start somewhere and we cant be expected to know everything straight away, it takes time. Definitely fast as it is compulsory for us to do it if we are healthy enough. If you know how to read the Quran, read as much as you can throughout Ramadan and if you dont know how to read it, spend these next few days looking for a teacher or beginners classes you can attend in order to read it in shaa Allah. Make sure you pray your 5 daily prayers and do dhikr (remembrance of Allah) after each salah (prayer). One type of dhikr you should do is recite Subhan'Allah 33 times, Alhamdulillah 33 times and Allahu akbar 34 times. Also repeat astagfirullah very often. Make a lot of dua, ask Allah azza wa jal (the Mighty and Majestic) to give you strength and to increase you in beneficial knowledge. Dont let shaitan make you think that youve bitten off more than you can chew, you can do it! I was very very far from the deen and now alhamdulillah i cover fully and try to be a good Muslim by staying away from whats forbidden and trying to do what we are told to do. Also if you havent already, make sure you read the Quran translation, it changed my life when i first read it. you can go on quran.com and read and/or listen. I also recommend that you buy a small book called Fortress of the Muslim which is filled with beneficial duas.
May Allah azza wa jal guide you to the straight path and keep you firm upon it-Ameen.
Finally another dua you should make very often 'O Allah Turner of Hearts, Make my heart firm upon your deen.' And during this blessed month repeat this dua 'Allahumma innaka afuwun tuhibuk afwa fa'fu ani