1Dont say militar say "military" NB the "a" is often silent.
This US use is coming into "Britspeak" aka modern/forward UK English. It always existed as an adjective "military uniforms" But now we also say "the military" as in The military tend to be more socially conservative.
My father is a military.
Trad uk use : The (+ or- Armed) services/ forces = (trad US) the military
--->A serviceman/men
CF a civil servant (funcionario)
For the Army :(tierra)a soldier, soldiers (To INCLUDE officers and generals) Eg Franco was a soldier.
For the Navy : Sailor (equally the same word for all ranks, rating to admiral) ( same word as for civilians, Columbus was a sailor)
The air force is new , but airman/men/woman/women exist
Lord Nelson was a sailor My grandad was a soldier/a sailor/an airman in WWI.
2. mind + ......ing
Not: mind +to infinitive
"I seldom mind hearing music" I Wouldn't mind another beer" "I wouldn't mind having one either!"
3. A long face= A sad face
Not everything is a false friend!
4. an sms on a cell(=mobile) phone -->to text , texting, texted etc.
I am unfamiliar with texting
I dont often text bkoz b4 4u k
5. formal clothes vs.casual clothes. but you can use informal