Hello and welcome to this wonderful game.
First, you jumped in to play the most difficult world of all, maybe a try-over in Beginnerīs World would be the better choice. This game needs some skill and a lot of knowledge (stated and acquired) to be learned before you really manage it.
Please make yourself acquainted with the manual, the first steps and the tips and FAQīs for Beginners you will find in the Forums (General and Beginners World).
We are willing to help if you donīt understand something thatīs written there.
Turn-arounds can be set obeying an indicator at what chance of delay you are operating.Many turn their birds at 1% chance of delays, but that is not necessary all the time.Those values also are valid at home base turns, where you you donīt set a turn-around, but calculate next departure instead.
Chances of delay are also for reasons you canīt control, like weather and traffic ,those will delay your flights additionally hazardously and influenced by location season.
There are ways to enhance the technical state of your airplane, click "maintenance" on your aircraft page. Generally you should not acquire any aircraft in bad condition, it will cause delays, cancellations and will keep Corporate Image of your company down, or you will have to repair it first costing time and a lot of money.