kesatu surat
Nama saya Sofia.
Aku ingin belajaran bahasa indonesia.
maybe you mean like this:
Surat pertama (my first letter)
Nama saya Sofia (my name is Sofia)
Saya ingin belajar bahasa Indonesia (I want to learn Indonesia language)
NB :
"aku" and "saya" have the same meaning
"aku" use for informal situation
"saya" use for formal situation
=>my english is not bad, but is not good too..so you can correct my english..^^