So I experienced my first loss today.
There's no shame in losing your first difficulty 5 game - it sounds like you did a lot better than I did the first time I attempted it. Once you get past 4, you start to get into difficulties where the AI civs have huge advantages to their science, culture, and production, so you have to be able to play quite efficiently to overcome the power gap they naturally have on you. Unfortunately that's also kind of restrictive in terms of options - the honor and piety tradition trees stop being viable first choices for example. You'll get the hang of it if you keep trying, and in a pinch it always helps to read about the common "meta" strategies.
I finally had some time recently to play some Civ 5. It's one of many games I've had sitting in my Steam library forever but never gotten around to. Short version: I love it.
I'm glad you're enjoying it! I thought it was funny how you ended up as the Ottomans with Austria nearby. Are you planning to do what the Turks never quite pulled off IRL and take Vienna?
As for me, I've been playing Civ V for just over two weeks now, so I started one last game to finish things off:
Map Type: Pangaea
Game Pace: Quick
Since I'm a Russophile, I decided to end things off with my favorite country. Russia's ability doubles its count of strategic resources and gives it +1 production from Horses, Iron, and Uranium. Depending a bit on luck, this can evaluate to a nice early-game production bonus, and with a lucky start next to a lot of iron and silver I easily became the highest-producing empire in the world, even scoring some early wonders like Hanging Gardens, Temple of Artemis, and Statue of Zeus. They also get a unique replacement for the Cavalry unit that's better at taking down weakened units and the Krepost, which is a Barracks that speeds the rate at which your cities acquire new tiles.
My plan was to shoot for the Domination victory, but I spent the early-game building up my cities and preparing. I met some of Russia's historical rivals like America, France, and Japan, as well as the Maya and Morocco. I was friendly with most of these until America got annoyed with me for extorting gold from city-states and settling too close to them, but this was measured because I wanted to knock them out soon anyway, and once I had the Longswordsman, Crossbowman, and Trebuchet units I declared war on the USA, which had the largest army in the world and access to their unique minuteman unit. It was slow going because my mainly trebuchet army took a lot of concentrated fire to bring down this special unit, but I eventually broke through and took Washington by employing a very Russian strategy: showing no regard whatsoever for the lives of my soldiers.
I stopped there, but with the strongest empire out of the way, a huge army, and snowball potential from all their wonders (including the ever-important Notre Dame) it would have been easy enough to take down everyone else.
Final Thoughts on Civ V coming up.
I'm playing every game from GotD 2020! Games Completed: 10/129
Currently Playing: Sid Meier's Civilization V