Beela,
1.you better do bring your clothes, as you will have a hard time to find anything here;
2. it is OK to wear a knee-length skirt and no pantyhose;
3. it is perfectly fine to wear your boots, as it's bloody cold in the winter here...I also love to wear my boots... but the "shorter skirts" you will mostly use for going out, like bars and pubs.. not during the day.
4. I don't think you will need all your 35 skirts. Bring some - the modest ones - for the office, and few-shoretr ones- for the night clubs...
5.I am not sure what company you are joining. If it's a Western Company, you can mostly keep your present clothes style at the office. If it's a qatari company, forget about open tops, you will need tops which are long sleevs,and close up to your neck ..
For more information please contact DaRuDe.. he is an expert in women's clothes, as well as in WOMEN in general..:)

Good Luck

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“You become responsible forever for what you have tamed”. Antoine de Saint-Exupéry