Why this script gets these errors?

Here is my script: Script to backup a directory

It gives these errors:

/home/sirakai/bin/backupdir: riga 14: [: troppi argomenti
/home/sirakai/bin/backupdir: riga 19: if[ -d /home/sirakai/Documents/ ]: File o directory non esistente

And then, my correct if:

Directory /home/sirakai/Documents/ esistente

It makes no sense because this path exists. It's my Desktop.