hi, if your game is running @ 90 fps or even @ 60 fps then you have issues that need to be resolved.
first, the temptation to use the Tick Event is what you need to avoid as much as possible. (there is also an editable/adjustable tick in engine now too, btw)
use Timers or Timelines or Custom Events whenever possible, to avoid Tick. (avoid it all together whenever you can)
with your game slowing down that much, you need to try to find what you are doing wrong as well, because it might not all be Tick.
avoid using the Delay node in the wrong place for instance, at times this can almost bring a game to a stand still. Also be careful with stuff like Shaders & Post Processing.
to avoid some of these things or to fix them, isolating them is about the only option. The Unreal Engine has many ways to do this, use of the Profiler is an ideal way, but to start with you can actually watch the game run in the Editor and actually Watch values, personally I love using Print String a lot just to see when & even how fast something is running or even if it’s working at all. (I know sounds too easy but it works)
another thing to keep in mind, is although we want everything in our games at once, all games & game engines have limitations on what they can do and we all have to be realistic and make compromises at least until we learn to do them better and faster. a major part game creation is all about being realistic, making choices and sometimes even compromises until we can do better.
a good idea is just do one thing at a time when creating a game, whenever possible, this way you instantly know when something is wrong.
all in all, I think that your problem is the Tick event and a possible solution is described above in the 2nd paragraph.
I highlighted in Bold most of the major points to make it easier to Google them (just search Unreal Engine 4 then the subject), you can also do the same in the Unreal Docs: https://docs.unrealengine.com/latest/INT/
hope this leads you in the right direction & helps, good luck. 