The bathroom is our private bathroom. We don't share with anyone. The only room we can get some extra space is garage. But I dont know how much it will cost to get permit and build the restroom out there.

Often, permit prices are listed online at the city or township web site. If not, you may be able to call and discuss it with the building inspector. Call early in the morning, before he/she goes out in the field. Is it feasible to steal the space for a shower out of the garage? Can it be done without ruining the use of the garage? Can the garage area be insulated enough that the drain and water will work well, or do you not live where freezing is an issue?

If it does not work out to use the garage to make the shower, it may work to steal 3 ft along that wall from the garage for a long reach-in closet for the master bed room once you use the other closet for the shower. That just takes some 2 x 4s, drywall, and insulation.

The problem I see is that you don't have room to make a proper bathroom. That closet will make you a shower, but it won't connect with the toilet and sink to make a bathroom without stealing a couple of feet from the bedroom. Can the bedroom spare that? Not really! Then your have to switch the position of the toilet and the sink. That is because you cannot walk past the toilet to get to the sink. The toilet also does not have enough clear space in front of it to be correct. It needs 21." It may work if you put the back of the toilet against the left wall and the sink where the wall between the two rooms are, and keep the shower to 36 x 42 or 48. You would have to measure. The door to the bathroom would have to be in front of the sink. Where is the door now? You may want to consider these:

Troyt White Corner 2-Pc Round Toilet White WaterSense Dual Flush · More Info

A corner toilet that tucks into that lower left corner.

40" Wall Mounted or Vessel Sink · More Info

And a wall-hung sink that is only 18" deep so that you can get around it. There are some wall-hung vanities that are this narrow, or just use shelves. Put a pair of med cabs sunk into the wall above and you will each have your own storage space. Notice that the sink will allow you both to use it if you need to, having two spouts.

Get the tallest medicine cabinets that you can afford, since the heights means more storage. The mirrored back is useful, too. allowing you to see at different angles for the light or to get out of the way of the partner.

Cove 16" x 36" Recess Mount Glass Shelves Medicine Cabinet · More Info

Be sure to check the depth, too. Don't settle for ones that are so narrow your bottles and cans won't fit! Check what size you need.You can place them close together on the wall and put wall sconces on either side and you will have great light for shaving or make up.

Forma Wall Sconce with Fabric Shade, Polished Chrome · More Info

You can pick up inexpensive ones meant for standard screw-in E26 light bulbs, then go buy LED bulbs for them and get more light with fewer watts. The bulbs should last you maybe 10 years.

But to be certain, you would have to graph the space that you have out on paper and see if you have room for moving around this small bathroom space. With a depth of only 38" wide, it may not be possible. Or you may be stuck with the toilet with its back against the left wall. A compact toilet is 27" long, plus 21 " in front of it gives 48". then you can put your sink. With a shower against the other wall, if you keep to a 36 x 36 shower, you will have 4' 2" between the shower wall and the invisible "box" in front of the toilet where you can't put anything. You would have to work out the door placement and swing requirements for a shower door (if you have one) to see if the 18" deep, 40" long sink can sit comfortable in front of the shower. If not, you go down to a single size sink, with some side counter, like

ConceptBaths Caen 32" Modern Bathroom Vanity Glossy White · More Info

Which is only 18.5" deep and actually has two drawers. It is 32" wide. Given the tight clearances in there, you might not want anything with corners, though! This set is shallower and has a narrow side closet that you can hang on the wall over by the room door.

32" Glossy Anthracite Bathroom Vanity Set · More Info

BTW, that room door is going to have to either be a pocket door or swing out into the bedroom. It is not going to fit into this bathroom with anybody in it.

Can you move your bedroom door? This is about the smallest, code compliant bathroom you can get...

Time to sell that house and move up to one that fits your current wants. There is no way to do what you want here economically enough, without negatively impacting the bedroom and closet space. You need a bigger house to have what you want.