Im in this beginners world and I've had a quick looks at your airline -
1. You dont want to be leasing new aircraft this early in the game world (especially in beginners world). There are tons of available and cheap planes of that type and OK they may be older and cost a bit more to lease but it does save a bit of money. Also when you spend money on new planes when you have just started, you have no wait (normally 3months) at least for the planes to come meaning you cant use the money to grow which is important at the start.
2. Some of your flight times are less than ideal. For most of (iff not all routes from your HQ) you will need to keep a minimum of 1 hour between your departures. Looking at your timetables, your first destination (Ankara) has flights leaving at 13:40 (GS007), 14:25 (GS015) and 15:00 (GS021). As there is not a large enough gap between departures, the system in effect treats them as the same flight and the number of pax you would expect to receive are divided between the 3 flights causing low loads. Tehran also has 2 flights leaving at the same time so this also needs looked at. You also dont want to be landing or departing during the night as the appeal to customer reduces during these times. Alot of your return legs are leaving at un popular times, generally between midnight and 5. If you look at some of these routes (Helsinki or Edinburgh for example) I bet your outward load is alot higher than your return leg.
3. From my experience mass reductions in prices dont give the boost in load factors to support the reduction. When your RI improves the load factors will automatically increase. I would look at setting prices back to default for a couple of game weeks. You may find your load factor may stay the same or slightly reduct but your income and profits should improve. Remember profit is the most improtant factor to aid growth.
4. Type of engine is not really important in terms of commonality. Most important thing is to try and keep within 3 types (OK I know I'M running 4 but for some reason I didnt get a big hit) as further fleets massively increase commonality costs.
5. Your marketing should be relevent to the size, age and type of airline you operate. For you I would be looking to have marketing of papers/billboards/radio/internet at your base city and nearby cities only. Run this until the CI growth slows (normally around 30) then add the same options for the next level and so on. These should always be run perminently.
Just a few pointers. Hope this helps.