If I had a time machine, I would first visit...

Actually travel to the future is technically possible (and not just at the usual one second per second rate). With a sufficiently fast spacecraft time dilation makes any future date achievable in an arbitrarily small amount of local time. There are just two problems. First you will need an unbelievably huge amount of energy to achieve relativistic speeds - far more than the mass-energy of your spacecraft - to go fast enough. Second it is a one way trip, so if you don't like what you find in the future there is no going back.

It might suck. The spread of Islam on the Arabian peninsula stabilized regional geopolitics, allowing for a blossoming of the academies. Today we enjoy the fruits of the works of many amazing Islamic philosophers and mathematicians, and the Islamic empires linked Europe to Asia, something it hadn't enjoyed for millennia. Without the combined efforts of Indian, Persian, Arabian, and European mathematicians and scientists, the world we know today might be far bleaker.

It might also be far nicer. It's tough to say. But I wouldn't presume that the rise of Islam was a net loss. I tend to think of it as a net gain.

Actually, I *did* learn Latin. My middle school offered it as one of the foreign languages needed to get an advanced diploma, so I did my three years.

We actually have a fairly solid grasp of how Classical Latin (as opposed to Medieval Latin or Modern Church Latin) was pronounced (and it helps that public schools teach Classical pronunciation). There are some ambiguities, some that we suspect changed over time, but it shouldn't be too hard to figure out - it's just an accent. You'll never pass for a native, but you can still speak the language fine.

As an aside, Medieval Latin was basically pronounced using the rules of whatever your native language was, so a Frankish Latin speaker would pronounce it differently from a Saxon Latin speaker (and yet it was still usable as a lingua franca). It's actually much more complicated than that, but that's a rough simplification.

Some scientists insist that although you could theoretically build a time machine, you can only go back as far as the moment it is first turned on.