hallo everyone, I'm a master in a campaign and I have a player who have a magus character, and he ask me that if he can use a greatsword and convine the next habilities, spell strike and spell combat, he said that he can take the greatsword with one hand and at the moment to cast the spell with spell combat, and then use the hability spell strike to hit the spell that he cast... is that posible?
He can do that with spell strike.
He can't do that with spell combat. That class feature specifically states using a light or one-handed weapon.
To clarify, with your example, he's actually just spell striking. One can take hand off weapon to cast touch spell, and then immediately put hand back on weapon to attack with it for the touch spell two-handed.
He however can't use spell combat with greatsword to attack at -2 penalty, let go with one hand and cast ranged or touch or any spell.
Nor could he be able to use spell combat and spell strike with a greatsword: attack at -2 penalty with two hands, then let go of sword with one hand, cast touch spell and attack with touch spell with two handed weapon.
he ask that if he can use spell strike and spell combat at the same round
He can't use spell combat and spellstrike in the same round with a two-handed weapon as he can't use a two-handed weapon with spell combat at all.
Spell Combat (Ex): At 1st level, a magus learns to cast spells and wield his weapons at the same time. This functions much like two-weapon fighting, but the off-hand weapon is a spell that is being cast. To use this ability, the magus must have one hand free (even if the spell being cast does not have somatic components), while wielding a light or one-handed melee weapon in the other hand. As a full-round action, he can make all of his attacks with his melee weapon at a –2 penalty and can also cast any spell from the magus spell list with a casting time of 1 standard action (any attack roll made as part of this spell also takes this penalty). If he casts this spell defensively, he can decide to take an additional penalty on his attack rolls, up to his Intelligence bonus, and add the same amount as a circumstance bonus on his concentration check. If the check fails, the spell is wasted, but the attacks still take the penalty. A magus can choose to cast the spell first or make the weapon attacks first, but if he has more than one attack, he cannot cast the spell between weapon attacks.
If he had a longsword or other one-handed weapon he also can't use it two-handed for spell combat. The ability specifically disallows two-handed melee attacks as the magus has to keep a hand free for the spell for the entirety of the full-round action.
If he uses a longsword in one hand the whole round, he can use spell strike and spell combat no problems.