Good initiative! Even though it will only benefit new users if everything else is also translated, which I imagine is already part of this project.
SOoo, I checked the Arabic translation and the outcome is fairly good, it requires some editing and few corrections to make it correct, smooth and consistent.
Here are the parts that didn't translate well, or at all:
Steemit
Steemians
NSFW ( the whole phrase was translated, but not the acronym of course)
No Cost to Participate
Upvotes
feeds
Feed
Resteem
curation
SBD
Live Help
Steem Blockchain
cloud-based
[...] treat it like a valuable!
URL
[...] your Blog post rewards and Comment post rewards
post promotion
Twitter
Facebook
platform
Downvotes
"When you are first starting out"
Tags
" attention-grabbing"
Steem Power
Steem Dollars
Steem Blockchain
the curators
in liquid STEEM/SBD
Power Up
Peerhub
BlockTrades
Bittrex
"Aiming for at least 50% your own words/images per post is" [...]
Get engaged
Flagging
New Member Support Community
Discord
"Their listing here does not constitute an endorsement or recommendation"
=> I hope this helped! Let me know if you need something other than assessing the translation of Google Translate :D
RE: Translation of the Welcome Page