Is there a good free gps app out there that i can write routes on to and use off line?
I use Komoot. It works really well, is easy to use, and works off line
Seconded. Komoot for me also. It's free for your local region and cheap if you want maps of most of the world. £29 or so if I remember correctly for the entire globe unless you're after maps of North Korea. I use it for following routes in the UK with voice turn-by-turn nav. I've also used it touring through France and Spain. It's routing is quite good and editing the route on your phone isn't overly painful unlike some other apps. There's also a website to edit routes on a proper computer which also works quite well on a phone.
OsmAnd is free and works well.
Komoot - free for your local area and works offline
Google Maps also offers offline nav but it will only work for on-road routes
The only downside with Komoot is that there's no option to set a privacy zone which means you should either start/end routes away from your house or not share them online.