OK so I pierced my tongue on the 5 of June witch makes thast 6day now and I just wanted to no when I can change the barbell shorter

Everyone heals differently and piercings heal from the outside. I personally tell evrybody to wait at least a few weeks before changing the jewelry. The good thing about an oral piercing is that they are the fastest healers. Go back to your peircer in about a week if you aren't comfortable doing it yourself.

For tongues it can take up to a few months to fully heal and even then the hole will close over very quickly.
For the first change it is best to go back to your piercer with your bar of choice and make sure it is appropriate for the healing you have done as well as the size.
Tongue rings are pretty hard to change the first time as the piercer will do it up very tight.
A friend of mine had his tongue pierced for 2 years and he took it out one night because he had been drinking and the next morning he could not get the bar through.

They say 6 to 8 weeks.