Overheating

Ford mondeo 2001 2.0 any advice, complete novice to engines! I got my car from auction eight wks ago. all good, on my way to work one night the car overheated into the red. Got help and plenty of water it was good to go. 5 weeks on... stuck on motorway on way home from work, two and half hour drive and eventually 30mins at standstill the car coped well. half way on temp gauge. Once home had to pop out again in local traffic 5mins in the gauge was in the red.... pulled over, gently undone water thingy and after a lot of coughing and water spluttering discovered there is water almost full. I left the car all day and checked water again and it was just a dribble lower than max. please can anyone advise too scared to drive and very broke, many thanks