1. is the installation and the registration [emphasis mine] in the software require internet or it can be run and register on offline?
Do note that there
is no registration. There are no accounts, no KYC, no servers. It's just a program running on your (and other people's) computers. If I place a Bitcoin buy offer on my PC, your software will pick it up after a while and display it to you. Then you can decide to take that offer and we do this trade person-to-person / peer-to-peer.
2. does Bisq software accept other currencies apart from USD? Because from my research I saw only usd with btc exchange
2. You can trade almost any Fiat currency for BTC, not just USD. There are plenty of digital payment methods that work well with Euros. One in particular, Revolut can be used to convert many Fiat currencies to Euro, which may give you more flexibility if your national currency only has a few offers.
Do keep in mind that Revolut was
recently hacked and massive amounts of customer data was leaked. If you can use a different payment method, I'd recommend that.
The current markets can be viewed on this webpage (and in the application):
https://bisq.markets/marketsIt includes lots of currencies like Japanese Yen, New Zealand Dollars, Hong Kong Dollars, Indian Rupees, or South African Rand.
3. will I buy the software key before the registration? and finally
3. can you please provide the link to download the software because I don't want to download the fake one and be scammed.
The software is free! Official URL is always
https://bisq.network/ and the downloads can be found either on
https://bisq.network/downloads/ or on their GitHub page where the full open-source code is released, as well:
https://github.com/bisq-network/bisq/releases/