i am new to the piano.but i have a touch with piano since i was 6 years old but i am unable to play with both hands now i am 18 years old .last year i got a 100 year old piano it was in unplayable condition i have a key board but the keys are very small i gave the piano to restoration .i have to wait 1 more week to complete it until then i have my keyboard to practice .i never took a piano lesson .but i can almost play any songs with my right hand to the ear.i started to learn Santorini by yanni with both hands .from youtube.i just need to practice the left hand as i never took a proper piano lesson.with my right hand i can play santorini too but its not so nice without left hand once i get my piano back will it be dificult to pracice after playing with keybboard???

You seem to have two questions here. First, you wonder about playing with both hands. This comes with time. Practice each hand separately at first, then gradually put them together--going very very slowly. As you get comfortable, pick up the tempo.
Do not try difficult pieces at first. You should, at this stage, be playing pieces that have only one note in the F and one note in the G clefs. Something by Yanni, unless it's been arranged to be very simple, is probably beyond you.
Your second question regards playing a "real" piano after a keyboard. Yes, it will be more difficult for the first couple of days, but after that it will be much easier! Trust me.

I think whether you use an acoustic or digital piano, can still train hand independence and coordination.

I am newbie and self taught too. I practice hands together like this:

1. RH. Play from memory.
2. After play fluently, use a metronome. Set to a lower speed, which you feel comfortable and have consistent playing.
3. LH practice, same as RH. Practice RH and LH alternatively.

Use metronome for LH is very important. For most piece LH is slower, may up to one measure per note. Its easily play LH too fast, RH too slow.

4. Play both hand together, without metronome. Just note by note coordination.

5. Finally HT with metronome.

This seems very slow in beginning, after a few songs, the progress become faster.

Another important technique is mental playing. It had been mentioned many times. Always bring along the music sheet. While in bus, visualize your playing, note by note in slow motion.

Thank you for reading.

Are you working with written pieces, too? That is, do you play from score, reading notes?
I think it's very hard to learn how to synch both hands properly by just watching someone play an advanced piece.