Sugestão de tradução:
"O que eu estou fazendo? Você está empurrando contra a mesa."
"Contra quem esse país joga futebol? Este país joga futebol contra ..."
"A cadeira está contra a parede? Não, a cadeira não está contra a parede; Está perto da parede."
"A cadeira está contra a parede agora? Sim, a cadeira está contra a parede agora."
Look: Against is a preposition meaning "in opposition to; in contrast to..."
1. In opposition to.
The fight against crime.
He decided against immediate publication.
Swimming against the tide.
1.1 In opposition to, with reference to legal action.
The first victim gave evidence against him’
1.2 In opposition to, with reference to a sporting contest.
The championship match against Somerset.
2. In anticipation of and preparation for (a problem or difficulty)
He gritted his teeth against the pain.
Makeshift barricades against tank attacks.
2.1 In resistance to; as protection from.
He turned up his collar against the wind.
2.2 In relation to (an amount of money owed, due, or lent) so as to reduce, cancel, or secure it.
Money was advanced against the value of the property.
2.3 (in betting) in anticipation of the failure of.
The odds were 5–1 against England.
3. In or into physical contact with (something), so as to be supported by or collide with it.
She stood with her back against the door.
Frustration made him bang his head against the wall.
4. In conceptual contrast to.
The benefits must be weighed against the costs.
4.1 In visual contrast to.
He was silhouetted against the light of the stair window.
Source: Oxford Living Dictionaries
"Espero ter ajudado."