iPhone 7 unavailable after forgotten password

so basically I forgot my password and I tried and tried but it showed iPhone unavailable so I’m kind of stuck and I don’t have a Mac and the phone was given to me by my dad but he didn’t tell me his Apple ID password and he died so I’m really stuck cause I don’t know what to do yea and also this is an iPhone 7 and please help me out

[Re-Titled by Moderator]