Turkce Gun iki

Merhaba arkadaslar!

Please correct or help me to say a few of these ideas / thoughts better.

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I feel bad these days, I don't feel or I don't do so well...

Bu gunlerde, ben kötü hissediyorum. You don't have to say 'ben' because you already mean that with the suffix 'um'. Also, you can say 'bu aralar' as an another alternative.

There are two ways, I think, to say that I have a head or stomach ache...how to say,

'My stomach has pain' and 'My stomach IS paining'

Is this correct?

Benim karnim agriyor vs. Benim karın agrim var. Both of them are used. Again you don't have to say benim here. 

Do you have a lucky number?

Sende, bir 'sansli number' var mi? Şanslı bir numaran var mı? But we prefer to say 'uğurlu sayı' rather than 'şanslı sayı/numara')

My cat is mixed colours / multi-coloured.

Benim kedim karisik rengi. Kedim karışık renkli or Kedim alacalı. 

How can I say this quotation or phrase:

'Imagination is more important than knowledge'?
Hayal gücü bilgiden daha önemlidir.
Diabetes, turkce nasil diyorsunuz?

Seker Hastalığı. Ben seker hastasıyim, onun icin ben sekerli yemek yemem.

I wish I had green eyes like my cat!

benim kedi gibi yeşil gözleri olsaydı! Keşke gözlerim kedim / kedimin-ki gibi yeşil olsaydı!
Kediminki, means ''my cat's''. Mine- benimki, yours-seninki. You can say 'my cat's' instead of 'my cat's eyes' right?
How can I say to try something, as in food:
Try means denemek in Turkish, and you can use it while talking about foods.
'I would like to try visne receli, and gul receli.
Vişne reçelini ve gül reçelini denemek isterim.
Turkey is so interesting and special because it is located in both Europe and Asia.
Türkiye çok ilgi çekivi ve özel çünkü hem Avrupa hem de Asya'da yer alıyor.
Turkiye Ulke, cok enteresan ve ozel cunku, hem Avrupa hem Asya da oturuyor.

You can't say 'oturmak' while you're talking about location of a country/place. The word ''oturmak'' is used for 'people'.