Title:

1) You should probably withhold the "no.1" until you've composed a second string quartet.

2) Since pieces for string quartet are commonly called string quartets, you should probably also omit the "For".

Instrumentation:

String quartets usually comprise two violins, a viola, and a cello. Variations are possible, of course, but a double bass is likely to overpower the other instruments (which is why in an orchestra there are many more violins than the there are double basses).

Notation:

1) The viola uses the alto clef except when its part is very high.

2) You need a time signature.

3) In 4/4 you should normally show beat three: This means that in m.5, for example, the violin and viola parts instead of having three eighth notes followed by a half note and another eighth note should have four eighth notes, the fourth tied to a dotted quarter, and then another eighth note.

Scoring:

1) Most of your triple stops (three note chords for one instrument) will be very difficult or impossible to play, especially the cello triple stops.

2) A cardinal rule of string scoring is that you should never have two violins play a passage in unison becomes there is bound to be disagreement in intonation (three or more violins playing in unison is perfectly fine; in this case the intonation differences tend to balance each other out to create a "chorus effect"). The timbres of the violin and viola are similar enough that having a single violin and a single viola playing a passage in unison will give you approximately the same undesirable effect.

Recommendation:

The main thing to remember is that you can't judge the sound or the playability of a piece from a MIDI sequencer mock-up. If you're serious about composing, buy a copy of Walter Piston's Orchestration and a copy of The Norton Handbook of Musical Notation, and write for real musicians that you personally know, listening carefully to their comments and, especially, their playing of the piece--and don't wait until you've finished to consult them; consult them along the way.

I'm replying here rather than on your user page because there I'm limited to 1,000 characters--or something.

Re: "I named my piece to 'For string quartet no.1' 'cause I didn't find a better name."

Names are tough.

Re: "I used treble clef without alto 'cause I play the piano and I can't read it."

Couldn't you make two separate scores then, a "short score" with fewer staves and only treble and bass clefs and a full score with treble, alto, and bass clefs?

Re: "I'm not an orchestrator , I'm 17 and I'm still learning the art of composition. It's my hobby and sorry for I'm and my pieces are not perfect enough."

Your errors in and of themselves don't really worry me (although I think someone did need--at least eventually--to point them out to you). You could easily have made them writing from the piano only, without the intervention of a sample sequencer, and I have little doubt they have been made many times before. Since the piano sounds nothing at all like a violin or viola, and so on, though, you couldn't possibly have been so deceived about them without the intervention of a sample sequencer.

Re: "I dindn't write my pieces to someone perform it."

THIS is what worries me. ALWAYS write for performers. NEVER write for a sample sequencer. It isn't a violin, and it isn't an instrument in its own right either (unlike, for example, an analog synthesizer or a Rhodes electric piano). Were dealing here with phony, fake, violins (and violas, and so on). That doesn't mean you can't use a sample sequencer as a tool; it does mean you can't write for it without turning yourself into a fraud.

Re: "I've never played the cello only the piano and I can't imagine how difficult is to play it."

Fine, but it's your job to find out. I'm perfectly willing to help (when I've got time), and the cello forum members probably are too.

I'd be very glad if you weren't tell me who am I ought to write my pieces.

If you don't want comment, don't ask for it.