I’m not an expert with liveries. My bad guys . So could you help me with something realistic enough?
To achieve realism, scrap the whole concept and start again. Let me explain:
About the Carrier: Flag Carrier from United Arab Emirates
The UAE can't really have a flag carrier in the same way British Airways or Air France are flag carriers of Britain and France. The country is actually the United Arab Emirates, meaning its a collection of smaller states, like the USA. While the United States has three main legacy carriers in the form of United, American, and Delta (and many more before that, see Northwest, Pan Am, Eastern, etc) none of them are flag carriers, and while all three do try to represent the country in some way, they fly from many hubs across the country. The UAE, meanwhile, is a rather small country, with only three major international airports - Abu Dhabi, Dubai, Sharjah (four if you count Dubai Maktoum, but that's mostly cargo at this point).
As Abu Dhabi, Dubai, and Sharjah are the three largest and most significant emirates, they each have their own airline - Etihad in Abu Dhabi, Emirates in Dubai, and Air Arabia in Sharjah. While Etihad and Emirates try very hard to represent the emirate they are based in, Air Arabia is mostly just an LCC so I won't discuss it here. Basically, Abu Dhabi with their 'from Abu Dhabi to the world' slogan and Emirates with its massive presence in most of Dubai's infrastructure have worked hard to establish themselves as the flag carrier of their own emirate, but not of the UAE in general. In fact, in my opinion, it would be impossible to have a flag carrier for the whole country - not because it is too big and diverse, like the US, but more because of the separation between the two most important emirates, which would mean that any major carrier could really only be the flag carrier of either Abu Dhabi or Dubai but not both. Additionally, a large part of traffic passing through AUH and DXB is connecting passengers, so attempting to start a true flag carrier operating from both airport would not work because having connecting passengers exit the airport, take an hour+ long bus ride, then go through another airport, would destroy the business.
This is already the name of a low-cost airline in the United States (which I really hope you already know...), and anyway can under no circumstances be used as the name of a flag carrier. It's a generic, meaningless name that does not represent the UAE at all.
Colors: Dark Single Color ( RED/BLUE)
Logo: Something Abstract on the tail section and Spirit Air written along the fuselage
Again, what's with the colors man? Just like the name, dark red and blue do not represent the UAE at all. Red, ok, maybe because its on the flag, but where did you get blue from? And while the idea of something abstract, which has worked pretty well for Etihad, isn't bad by itself, it would not work at all with the colors you want. Finally just want to reiterate how terrible of a name that is...
And finally, the 737-400. Really, it's not that useful of an aircraft in most cases, and especially not in the UAE. Where could the range of a B734 get you from there? Bahrain? And why would a flag carrier of one of the richest countries in the world - per capita and in general - be using an outdated aircraft from the 80s when there are vastly superior modern similarly-sized planes available?