Congrats on wanting to ride again.
If I were in your position, I'd inflate the 25mm tyres to around 80-90 PSI (or if you have the 32mm stock tyres go for perhaps 60 PSI) and then do a basic M check to make sure nothing's loose and that the brakes work as expected.
Then go for a slow gentle ride from your home up and down your street, perhaps a hundred feet, or a hundred metres. You'll probably notice something that needs tweaking, so do that, and put the bike away. This is probably 5 minutes riding total.
NEXT DAY, do it again. Go ride down to the corner, the nearest intersection or a feature like a park or a particular tree or something. There's no rush, ride at walking speed if that's comfortable. Then return home. You could follow a different route home, if feasible. 10 minutes riding or so total.
By this stage, you should have some confidence that the bike isn't going to collapse under you.
THIRD DAY, Pick a place you want to go, that is 10 minutes each way. Go there, do the thing, come home. This is the start of a habit, taking the bike to do something instead of driving.
Make this habit stick - ride every day for a week and it starts to become normalised.
Don't worry about speed, that comes later. Don't care about fancy bike clothes or shoes or whatever, your normal daily `round-home wear is going to be fine to get started. And remember your bike route doens't have to be the same route as you'd drive in a car - it's fine to take a quieter and more scenic route.
I was 120 kg in 2013 when I got back into riding. Too many pies at the office job, and too much desk/screen time. I was riding a steel MTB and it coped fine for years, until I bent the seatpost by having it up too high.
Your bike will be fine for any normal street riding. Just remember to not ride it off kerbs/curbs like a 10 year old on a BMX, and for comfort try and not put all your weight on the saddle (its not a seat, its a saddle) Some small amount can be on your arms, but your weight should be taken by your legs as much as your butt.
The existing solid fork should be fine for your initial return to riding - suspension is generally not needed on streets. If you can walk a path normally without looking at the ground, you can ride that same path with no suspension.
Once you have a couple months riding under your belt, then decide if you want to keep riding road and what about this bike annoys you or detracts from your ride.