when i play arpeggio in high positions, either i dont have tone because my left hand is relaxed, or its stiff because i`m traying real hard to press strings. Any suggestion how to improve this?

maybe your strings might be too high above your fingerboard. try your friend`s violin and see whether it is easier on theirs.

You do not need to relax or tighten your hand ... play normally! Higher positions don`t need to be intimidating. Simply anchor your thumb at the bottom of the neck (most violins have a place where a thumb fits nicely) and move slowly up the string. Be sure not to release your first finger so you can continue to stay in tune while coming down. When you become confident in your tonality, you can add vibrato.

Better tone can be heard if you practise the higher notes with the bow near the bridge. Basically, the sound box can get more sound to echo around in it, if you play near the bridge.

About the stiffness, its all about the height of the bridge and strings. Sit down and work out how lightly you have to press each string down to get a sound without any harmonics. Then practise your arpeggios at that level (without vibrato, so you get the exact note). You will be able to move faster and get more confident at placing your fingers.

Soon, you will be able to apply more pressure to get a good vibrato, and get a softer tone by playing away from the bridge.

Jay