Hi

I use a 4g router in my home.  I need to have the router upstairs at the front of the house to get a decent signal but this gives me reasonable wifi coverage throughout the house. I am now looking to extend wifi out to a new garden building at the back of the house (only 5m away) and I thought a mesh system would be the easiest way to achieve this, allowing me to boost the signal at the rear of the house so that it could cover the garden building and/or adding another unit in the garden building.  I wasn't sure how easy it would be to connect a mesh system to my existing EE 4g router so I have invested in a Deco X50-4g router plus 2 further X50 units as satellites.

I found it easy to set up and had no trouble connecting the satellite units to the 4g router whilst in the house.  But I have two problems: 

1. Download speeds within the house are much lower with the X50-4g router than my original router.  I had hoped they would be better.  I'm only getting half the download speed (around 20 MB/s compared to previous 40-50), though oddly upload speeds are much better.
2. I am still getting no wifi in the garden building from the satellite unit placed at the back of the house - so no signal across 5m even though walls between are just timber frame - and when I take a satellite unit out there it can't find a connection (red flashing light).

Can anyone offer me any advice on either point?  I'm wondering if I've bought the wrong units - should I have bought a PX50?  I wasn't sure that powerline would work.  The garden building is connected to the same meter but I think probably on a different circuit.

Thanks