Sorry, but this game is terrible.
To start with the game is visually boring- the first thing you should do is improve the graphics. You can still keep the graphics simple, but just maybe add a few more colours or pictures.
Then there is the fact you have to go back to the start every time you get a question wrong, which is really irritating. Try adding a save button, or tally-ing up the answers, with a review of how to improve at the end. This will mean people don't have to constantly redo questions to get to the end.
Next is the fact the quiz is way too short. A good quiz has at least 10 questions. The fact that there are only 6 (7 if you count the shooting part) questions means you're providing little entertainment, because there's little to be entertained by. Use you imagination, and add in a few more questions.
Then there is the fact I disagree with many of your answers, as does many other people and zombie survival guides. You seriously need to review your answers. Here's a question by question explanation as to why you're answers are wrong:
Q1- Sometimes you do have to abandon friends. However, there is a benefit to saving them- later on they can be useful. They can help gather resources and fight zombies. Who knows, they might even save you later. So if it's not too perilous, you obviously want to save your friend. All you friend has done if trip up, and they're probably still right behind you, so it's not going to be very difficult to save him while keeping yourself safe. I think you need to change the question so it's clear that saving your friend is dangerous and will probably kill you.
Q2- Ah, the age old question of where to go in a zombie apocalypse. Now I realize where to go in a zombie apocalypse is under a lot of debate, and really it depends on where you are when the apocalypse starts. But unless you're super close to a weapon shop, it's a bad place to go. Because that is where everybody else will go. More people= Less supplies, more people to turn to zombies, more bait zombies will be attracted to. You can find a decent weapon in many other places, without going to the fatal weapon shop. Going home, however, is a good idea a lot of the time. Most people's homes will have enough food rations for 6-14 days, plenty of junk to use for barricades. plus several items that can be used as weapons (kitchen knives, gardening tools, sports equipment). Also, you will already be familiar with the layout, a major advantage. And most importantly, there will be few people at your home. The church is still a bad place to go, for even more reasons than you mentioned. I think you need to make home the right answer, or change your options so the answer would be something the majority of people can agree with.
Q3- Firstly, I highly doubt that these are the only 3 things you would be able to grab in a WEAPON shop. But obviously these are all 3 option answers, so let's just roll with it. The gun not being loaded thing makes sense. But why does the katana have to be attached to the wall? There is no law saying katanas must be attached to the wall, and you gave nothing to hint that it would be. I think you either need to make it obvious the katana is attached to the wall (because it's something silly to just assume), or make the first two options guns.
Q4- To start off with, I live in the UK, guns would be a definite no-no in a zombie apocalypse. Because even if I do manage to find a gun, there's no way I'm going to get enough ammo for it to be useful. But I'll just pretend I'm in America. In which case I still disagree with you. With guns, a lot of it comes to preference and ability. If you're not experienced with guns, I feel an MP5 would be better. It's light, has low recoil, and it's rapid fire means an un-experienced person will probably find it easier to get a hit with it. Of course, you still have the problems of power and ammo, but it will do the beginner gun-user more good than the shotgun, due to it's heavy recoil, shot spread, and low ammo capacity. But for somebody who has gun training/experience, these disadvantages will not be a problem, so the power of the shotgun will make it better than the shotgun. So the answer will depend on the person's experience with guns. Maybe you could have a pre-question asking the person's experience in guns, or have a set amount of experience stated in the question. Also, why a katana in particular? Just wondering. I personally would be more likely to go for a machete. A katana isn't really an ideal weapon if you're not trained in using them. But I don't suppose it matters, the katana is not the deciding point in this question.
Q5- NEVER EVER GO TO THE MALL IN A ZOMBIE APOCALYPSE! Unless the apocalypse has started in the dead of night, then a mall will jam-packed full of people. And as we all know, more people= less supplies left, more people to turn into zombies, more zombies attracted. Seriously, everything there is in a mall you can find elsewhere. There will be plenty of food in normal nearby houses, people do keep food in their kitchens. You can find a safer amount of people in various other places. Then there's the fact the mall has so many wide entrances and windows that it will be impossible to barricade. So instead, make home the right answer, or get rid of home and add in a new correct answer.
Q6- Well, I actually agree with this one. So long as you do it politely. XP
Q7- The command to 'press space to shoot the zombie' needs to appear quicker.
Finally, just do a basic grammar check before you publish a game. Proper spacing, capital letter, and full stops are vital elements to a good game. Without them your game seems sloppy, and people will negatively pre-judge the content.