Hello! The answer depends on your native language, your knowledge of other Slavic languages and so on... Now I'm doing a practical work at university related to Russian as a foreign language. I've been to classes and the first thing I've noticed was the bad pronunciation. In principle, students used the proper grammar, but sometimes it was impossible to understand them :( The phonetic system, well, may be a bit unusual, all these soft and hard consonants and unpredictable stress. But I strongly believe that phonetics is always specific for every language. The slight accent is OK, but it's very important to learn the basics of phonetics to be understood by others. 
At the very beginning, the grammar may seem easy. For example, if you want to ask where the shop is (grocery, whatever), you needn't know even any verb or word order or something like that, you can ask literally 'where shop?' or 'where here shop?'. But then it becomes much heavier. For example, when you learn that there are two where-s in Russian: one 'where' is for location (где), and another is for orientation (куда), as in German 'wo' and 'wohin', and the whole case system makes a distinction for the location and orientation of the object. It's only the example, maybe it would be very easy for you, maybe not.
Anyway, I wish you good luck in learning Russian if you want to learn it :) 
UPD: Forgot to write. The tense system is very poor, there you can't find anything hard. But: perfective and imperfective aspect. It affects almost the whole verb system, and for foreigners, it's very complicated where and which aspect to use because it correlates not direct with the tense. 

ما تحطنا انتا في الصوره بقى يا باشا

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