GRAMMAR

PRESENT PERFECT: USES

1) Actions that start in the past and continue in the present.
    "Jane has lived in London since 1996".
2) Actions that happened in the past and have some kind of effect or relevance in the present.
    "Paul has lost his wallet. He needs to cancel his credit card".
3) Actions that can be resumed.
    "I haven't finished reading the book".
4) Actions that just happened, recent actions.
    "They've just bought a new car".
5) Actions about life's experience.
    "I've never tried parachuting".
 
CONDITIONAL SENTENCES

TYPE	FORM	USE	EXAMPLES
0	IF + PRESENT SIMPLE ↓ PRESENT SIMPLE	-  UNIVERSAL TRUTHS             -  FACTS	If you heat ice, it melts.
1	IF + PRESENT SIMPLE ↓ ‘WILL’/’WON’T’ + INFINITIVE	-  POSSIBILITY IN THE   FUTURE, UNDER CERTAIN CONDITION	If I travel to London, I will visit the Big Ben.
2	IF + PAST SIMPLE ↓ ‘WOULD’/’WOULDN’T’ + INFINITIVE	-  HYPOTHESIS	If you were a bird, you would be able to fly.