I left out the following sentences.

Please, could you check them too?

1) My backpack is very heavy because inside (in it? are both possible) there are extra clothes, food, water (or food and water) for two days, a map, and a compass.
2) I'll take a big backpack with a tent to sleep in.
I'm wearing a mimetic (??) T-shirt and a pullover (jumper) over it.
3) On my shoulders I'm carrying (not I'm wearing a bag with a compass, extra food and clothes.
4) How are you planning to organize the email partnership?

1. "in" or "inside" are both fine.

2. mimetic???
http://www.thefreedictionary.com/mimetic

"pullover" (not "jumper")

3. Yes, "carrying" is correct.

4. OK

1) Both options are possible. You can say "My backpack is very heavy because inside it there are extra clothes, food, water for two days, a map, and a compass." or "My backpack is very heavy because inside there are extra clothes, food, water for two days, a map, and a compass."

2) Great! You can say "I'll take a big backpack with a tent to sleep in." Additionally, you mentioned wearing a "mimetic" T-shirt. This term is a bit unclear, so it would be helpful to use a more specific word to describe the T-shirt if possible. Lastly, you mentioned a pullover, which can also be referred to as a jumper.

3) Instead of saying "On my shoulders I'm carrying," you can say "I'm wearing a bag with a compass, extra food, and clothes." This clarifies that the bag is on your shoulders and contains those items.

4) To organize the email partnership, you can consider the following steps:
a) Define the purpose and goals of the partnership. Determine what you want to achieve through the partnership and how it aligns with both parties' objectives.
b) Identify potential partners by researching organizations or individuals who have a similar target audience or complementary services/products.
c) Reach out to potential partners via email and introduce yourself and your proposal for a partnership. Clearly explain the benefits they would gain from partnering with you and how it would be a win-win situation.
d) Negotiate the terms of the partnership, including responsibilities, expectations, and any financial or logistical arrangements. Ensure everything is thoroughly discussed and agreed upon.
e) Create a partnership agreement or contract outlining the agreed-upon terms and have both parties sign it.
f) Implement the partnership by coordinating marketing efforts, sharing resources, and collaborating on projects.
g) Maintain regular communication and continuously assess and evaluate the partnership's effectiveness to ensure it remains mutually beneficial.