Decrypt files encrypted by ransomeware

I am developer myself, My PCs is infected by a ransomeware. many files are renamed also for some files internal content is also decrypted, while somefiles content is not changed (only renamed).

renaming is not an issue, it renamed just by postfixing a random string to oldname like
readme.txt is renamed to readme.txtasdjh892hdiu93748hf34h34hf34.abcd
index.php is renamed to index.phpasdjh892hdiu93748hf34h34hf34.abcd
same postfix is added to all filenames. so recovering original filenames will not be an issue

I had backup some files before so I can provide (before and after) versions of some files, so that you can make comparison and trace nature of changes or decryption algorithm.

Need key or algorith to decrypt it back.