Should any crucial issue (arise from) the negotiation with the foreign company immediately report to the general manager for advice.
改变一下结构：
If any crucial issue should (arise from) the negotiation with the foreign company, immediately report to the general manager for advice.
前面是虚拟条件句的倒装句,表示对将来事实相反.（说话者期待没有问题出现）后面是祈使句.
万一与国外公司的谈判上出现重要问题,立刻向总经理报告寻求建议.