ok so what about money? Because now I am -5 per turn and a few turns ago I was +50 I don't understand how money works in this game
I'll make some guesses, but I can't say for certain not knowing what's going on.
First off, click on the gold counter on the top menu bar. This brings up a menu telling you your per-turn income & expenses (broken down by units, buildings, and tile improvements - roads).
+ Military units. Each unit has a maintenance cost. If you are taking enemy cities, it sounds like you have a good-size military - maybe bigger than you can afford.
+ Do you have markets in all your cities? You have to keep up with the economic improvements or else you'll fall further & further behind as buildings & units get more expensive.
+ Trade routes between cities & your capital are a huge source of income for a large empire. You need roads between each city, or harbors in coastal cities. However, roads cost gold each turn now - 1 gold per tile. So you can't have roads going all over the place or else your road costs will sink your trade income. Build one road between each city as directly as possible, and that's it. I.e., Antium links to Corinth which connects to Rome, so both Antium & Corinth are connected to the capital (you don't need a separate road from Antium to Rome).
Since you mentioned your empire forms a giant ring, I suspect road costs are part of your problem.
+ The cities you just annexed may have a lot of expenses and, if you haven't built courthouses yet, you may not be getting any income from them yet.
+ When you change eras - Medieval to Renaissance, etc., it changes your income & expenses, though I haven't investigated exactly how. So you might have gotten caught on the wrong end of an era change along with other existing economic problems.
Those are the major potential issues off the top of my head.