so here goes my first post,as the title might hint, i'm going to buy a bike, i havent had a "real" one from since i was a kid
i happened to ride a friend's 28" road bike one of these days and made me fall in love with the sport again...
im living at a city, country's Greece
i am looking for something cheap, while at the same time being able to be somewhat useable in both Off road and On road,since at holidays i happen to be going at the mountains(villages)
sure, you could say that a cheap ATB/MTB isnt a real ride, but thats what my wallet can afford at the moment, and since its the first bike ill get, i dont feel like spending lots
i weight 60kg/136LBS
my height is 178cm...or else 5 ft 10 5/64 inch
so here are the specs of the one i resulted in to and thinkin of buying :

Frame : HI-Ten 48cm / 19”
Fork : Zoom 386 ,60mm
Derailleur : Shimano RD-TX35
Shifter : Shimano ST-EF51
Brakes : Tektro v-brakes
Freewheel : Shimano TZ21
B.B set : Neco
Rims : Mach1 double ER28
Weight : 18.0

its a 29" ATB/MTB with knobby kenda kadre tires at the low price of 240$
my number 1 question is, is it really worth getting it? at that price of money?
as i stated before,im living in the city, so ill be riding it at the city a lot too and might try to get into group rides
will i need to change the tires into slick road like ones?
if so, what are some cheap ones,and what size should they be? will 28" road tires fit in it?
and will i be able to catch up to the 28" road bikes with em?
i heard the bigger the tire the faster it goes,so i wouldnt rly want to go for a 26" mtb at the city,altho i guess it would do better at turning left or right

regarding the holidays now,i dont think i will be doing anything extreme with it,not like it can anyway since its actually cheap...i might try to get into some forests or some trails but will it be safe? or would i trip on ever little stone i might step onto? should i change the suspension to a higher mm when i get there?

last but not least, the frame is 48 cm and i think its good for my height(178cm...or else 5 ft 10 5/64 inch) isnt it? some tests i've done says its ok but will the 29" tires make it uncomfortable for me?

im between this bike and a road one,but it would be a shame if the road one is useless at the villages i go to for vacations,i would want to ride my bike to the nature too

sorry for my english,it's not my native language and i hope for some replies to help me make my decision