I need to correct mistakes of website on magento cms

Hello!

My name is Kristina. I have made website on platform magento. But I am not pretty good in programming and I am having mistakes on site, which need to be corrected.

I need 3 things to be solved:
1) mistake:
not found: 1054 Unknown column 'FLOOR((ROUND((e.min_price) * 1, 2)) / 1000) + 1' in 'order clause', query was: SELECT FLOOR((ROUND((e.min_price) * 1, 2)) / 1000) + 1 AS `range`, COUNT(*) AS `count` FROM `kristinie_0catalog_product_index_price` AS `e`
INNER JOIN `kristinie_0catalog_category_product_index` AS `cat_index` ON cat_index.product_id=e.entity_id AND cat_index.store_id=1 AND cat_index.visibility IN(2, 4) AND cat_index.category_id = '93' WHERE ( e.website_id = '1' ) AND ( e.customer_group_id = 0) AND (e.min_price IS NOT NULL) GROUP BY FLOOR((ROUND((e.min_price) * 1, 2)) / 1000) + 1 ORDER BY `FLOOR((ROUND((e`.`min_price) * 1, 2)) / 1000) + 1` ASC

2) I could not enter admin panel. It is blank
3) I have mistakes of mixed content when opening site in https.