IS THIS GOOD OR BAD
I guess it could be either depending on the details/context.
If your relationship is based on trust and honesty it would be bad.
If your relationship is based on lies, it would fit right in.
If the religion you are faking conflicts with your own beliefs it would be bad.
If you have no beliefs, it might work, with a lot of work.
If you are faking it with some perverse idea of eventually changing their beliefs to fit yours, its kinda selfish.
If you are faking it to possibly convert your religion to theirs eventually, it could be a proclaimation of dedication.
If you're with this person, a person who is very demanding religiously, you might want to rethink your reasons for being with them.
Most people in healthy, happy relationships have alignment in the things which are important to them.
If you need to lie to align with them, you won't have a healthy, happy relationship.
If you choose poorly in alignment, misery is your future.
Choose Wisely