Do not take that advice please. If you can , meaning if you have the time
and will , please learn a little about testing telescopes and mirrors.

Great advice. You should check if your local club can assist you in
evaluating optics. Our club periodically runs a mirror making workshop
where there are a number of folks who have the skills and equipment to check
your mirror.

In any case, I would buy a good quality secondary. We have always had good
luck with Protostar, but I am sure that others are also good.

Dennis