For your first solo trip, it’s probably a good idea to choose a destination with a developed tourist infrastructure.
If this is your very first international solo trip, I recommend choosing an all-inclusive resort to stay at.
While traveling alone may seem lonely, you become more sociable and meet new people you wouldn't have otherwise.
First solo trip? Maybe start with something home so you can experience foreign culture without leaving the country.
Keeping your passport in a hotel safe is the worst thing you can lose, but you should also separate some of your cards.
It’s true that it’s better to be overprepared than underprepared, especially when you’re by yourself in a foreign city.
Even if it’s just ‘good morning’, ‘thank you,’ and ‘a coffee please,’ it will go a long way and make it more likely to get help or recommendations should you need it.