Alright, I'll try to do it sentence by sentence and to some extent I can only give a functional translation:
العرب من احسن خلق الله استعدادا
Arabs are among the best of Allah's creation when it comes to preparation.
فإن نافسوا غيرهم من الأمم في علم فما تقصر عن ذلك فِطَنهم
If they were to compete against other nations in knowledge, they'd never lack the mentality.
و إن سابقوا في الصناعت فلن تبعد عنهم غلية
If they were to compete in the field of industry, they won't lose to any purpose.
و إن عمدوا الى زراعة فهم أهل كدح و جلاد
And when it comes to agriculture, they are great laborers and forbearers.
و إن يروموا مراما فثقْ بانهم اولو عزم و همة
And if they aim for something, they will do their best to achieve it.
نسبهم عريق
Their history is great.
مجدهم اثيل
Their glory is firm.
فإن نهضوا اليوم فقد كان اول الناهضين
If they rise today, it's because they were the first to do it.
و إن اخذوا باسباب الخضارة فإنهم يسيرون على سَنين آباء عظام و اجداد كرام
And if they took the leads of civilization, it's because they are walking the steps of their great fathers and honorable ancestors.
و من خالجه شك في عظمتهم فليقرأها في صحائف الآثار
And those who may doubt their greatness should read in the pages of history.
* Their could be alternatives to my choices, but I tried to make it as clear as possible.
I hope it's of help.