Hello Dragan,
1) If export function is not exporting all products, then there can be a chance for PHP memory limit /execution time limit issue.
Please try increasing PHP memory_limit and PHP max_execution_time in server settings.
2) If updating only specific columns like post_status and visibility , then the CSV just needs 3 column for achieving it.
i) if its simple product, only sku or ID , post_status and visibility columns needed.
ii) if CSV contains variation also, then sku or ID , parent_sku or post_parent , post_status and visibility columns needed.
If the issue still persist, please send us the sample CSV to support.xadapter.com