I cant  understand why you want to do this job free  my friend. if you are enthusiastic and will be able to do so, you can search for projects that are new to it and make their translations. you can even make money.I am sure that you know that it is really hard to make money at this time.
it's a little absurd to me to give you free service in an area you think you can do really well.my advice to you. There are certainly good projects on the forum if you search. Contact the manager  .  Tell him that you can do it  to translate work.