You can double check the fall with your spirit level.
Install gutter downpipe.
Its easy less than 30 minutes and under 30 00 in parts.
How to add a downspout in an existing gutter step 1.
Place a step ladder under the area you are installing the downspout.
Measure in 4 inches from the end corner of.
Fit the gutter in place which normally just clips in with the appropriate stop ends connectors and gutter outlet for the downpipe.
Cut it to length with a hacksaw and removing any burrs with a half round file.