Hi, and welcome!🙂
Hypos can be scary, particularly for other people who are just seeing the effects. The thing to do is remain as calm as possible and check the blood levels using a meter - unless it's really obvious, in which case, treat straightaway and take the reading later. If the person is conscious, give some fast-acting sugar or glucose. People with diabetes should always carry something with them in case of hypos. Personally, I use jelly babies but there are also glucose tablets or sweet drinks like lucazade or regular (not diet) coke. If unconscious then you should ring 999 - don't try to give an unconscious person anything to eat or drink as they might choke.
Hopefully, your partner will recognise when his sugar levels are dropping low and can take action. Sometimes, when people drop low they can be aggressive and uncooperative, so you may have to be firm with them to persuade them they need to eat. It can take a little time to get back to normal after a hypo - you need to test the blood 15 minutes after giving sugar to make sure the level has gone up.
Hope this helps - and that it doesn't happen too often!