You hired cheap non English speaking people who have brought their own methods for this type of work, then its our fault, these methods are non standard to anyone here, this is a problem and I do sympathise with you ,I would be annoyed if I could not communicate and if I lost faith or was worried as you are that problems may be more apparent later, its best at this point to have a meeting with the company that you hired and get it all sorted out once and for all, it's your money, your house, all banter aside ,get it to some sort of order before your fears are realised, that aside ,it may turn out that they are doing good work, a panicking client with little knowledge is also un helpful