Hey Sajjaja, first of all, tell us your in-game name so we can add you to the clan.
You will find we are a fairly active bunch, and will usually have a few missions going on at once with squads.
For Excalibur, Concentrate on shields and power strength, use radial blind, and then melee away.
When playing Survival missions (the ones where you collect oxygen,) don't activate the oxygen pillars until your oxygen bar says around 60%, as it will waste the extra.
Get a sentinel asap, as they are invaluable assistance.
Don't buy anything using platinum just yet, just be patient, you can get everything you want, especially with the help of the clan.